Study on Climate Change in Southwestern China (2015)

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SpringerThesesRecognizingOutstandingPh.D.ResearchZongxingLiStudyonClimate ChangeinSouthwesternChina SpringerThesesRecognizingOutstandingPh.D.Research 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ZongxingLiStudyonClimateChangeinSouthwesternChinaDoctoralThesisacceptedbyColdandAridRegionEnvironmentandEngineeringResearchInstitute,ChineseAcademyofSciences,Lanzhou,China123 AuthorSupervisorDr.ZongxingLiProf.YuanqingHeColdandAridRegionEnvironmentColdandAridRegionEnvironmentandEngineeringResearchInstituteandEngineeringResearchInstituteChineseAcademyofSciencesChineseAcademyofSciencesLanzhouLanzhouChinaChinaISSN2190-5053ISSN2190-5061(electronic)ISBN978-3-662-44741-3ISBN978-3-662-44742-0(eBook)DOI10.1007/978-3-662-44742-0LibraryofCongressControlNumber:2014951737SpringerHeidelbergNewYorkDordrechtLondon©Springer-VerlagBerlinHeidelberg2015Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpartofthematerialisconcerned,specificallytherightsoftranslation,reprinting,reuseofillustrations,recitation,broadcasting,reproductiononmicrofilmsorinanyotherphysicalway,andtransmissionorinformationstorageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilarmethodologynowknownorhereafterdeveloped.Exemptedfromthislegalreservationarebriefexcerptsinconnectionwithreviewsorscholarlyanalysisormaterialsuppliedspecificallyforthepurposeofbeingenteredandexecutedonacomputersystem,forexclusiveusebythepurchaserofthework.DuplicationofthispublicationorpartsthereofispermittedonlyundertheprovisionsoftheCopyrightLawofthePublisher’slocation,initscurrentversion,andpermissionforusemustalwaysbeobtainedfromSpringer.PermissionsforusemaybeobtainedthroughRightsLinkattheCopyrightClearanceCenter.ViolationsareliabletoprosecutionundertherespectiveCopyrightLaw.Theuseofgeneraldescriptivenames,registerednames,trademarks,servicemarks,etc.inthispublicationdoesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfromtherelevantprotectivelawsandregulationsandthereforefreeforgeneraluse.Whiletheadviceandinformationinthisbookarebelievedtobetrueandaccurateatthedateofpublication,neithertheauthorsnortheeditorsnorthepublishercanacceptanylegalresponsibilityforanyerrorsoromissionsthatmaybemade.Thepublishermakesnowarranty,expressorimplied,withrespecttothematerialcontainedherein.Printedonacid-freepaperSpringerispartofSpringerScience+BusinessMedia(www.springer.com) Partsofthisthesishavebeenpublishedinthefollowingjournalarticles:1.*Li,Z.X.,He,Y.Q.,Wang,P.Y.,Theakstone,W.H.,An,W.L.,Wang,X.F.,Lu,A.G.,Zhang,W.,Cao,W.H.(2012):ChangesofdailyclimateextremesinSouthwesternChinaduring1961–2008.GlobalandPlanetaryChange,80–81(2012):255–272.(ReproducedwithPermission)2.*Li,Z.X.,He,Y.Q.,An,W.L.,Song,L.L.,Zhang,W.,Norm,C.,Wang,Y.,Wang,S.J.,Liu,H.C.,Cao,W.H.,Theakstone,W.H.,Wang,S.X.,Du,J.K.(2011):ClimateandglacierchangeinSouthwesternChinaduringthepastseveraldecades.EnvironmentalResearchLetters,6(2011)045404.(Repro-ducedwithPermission)3.*Li,Z.X.,Feng,Q.,Zhang,W.,He,Y.Q.,Wang,X.F.,Norm,C.,An,W.L.,Du,J.K.,Chen,A.F.,Liu,L.,Hu,M.(2012):DecreasingtrendofsunshinehoursandrelateddrivingforcesinSouthwesternChina.TheoreticalandAppliedClima-tology,109(2012):305–321.(ReproducedwithPermission)4.Li,Z.X.,He,Y.Q.,Theakstone,W.H.,Wang,X.F.,Zhang,W.,Cao,W.H.,Du,J.K.,Xin,H.J.,Chang,L.(2012):AltitudedependencyoftrendsofdailyclimateextremesinSouthwesternChina,1961–2008.JournalofGeographicalSciences,22(3):416–430.(ReproducedwithPermission)5.Yang,X.M.,Li,Z.X.(correspondingauthor),Feng,Q.,He,Y.Q.,An,W.L.,Zhang,W.,Cao,W.H.,Yu,T.F.,Wang,Y.M.,Theakstone,W.H.(2012):ThedecreasingwindspeedinSouthwesternChinaduring1969–2008,andpossiblecauses.QuaternaryInternational,263(2012):71–84.6.Li,Z.X.,He,Y.Q.,Pu,T.,Jia,W.X.,He,X.Z.,Pang,H.X.,Zhang,N.N.,Liu,Q.,Wang,S.J.,Zhu,G.F.,Wang,S.X.,Chang,L.,Du,J.K.,Xin,H.J.(2010):Changesofclimate,glaciersandrunoffinChina’smonsoonaltemperateglacierregionduringthelastseveraldecades.QuaternaryInternational,218(2010):13–28.(ReproducedwithPermission)7.Li,Z.X.,He,Y.Q.,Yang,X.M.,Theakstone,W.H.,Jia,W.X.,Pu,T.,Liu,Q.,He,X.Z.,Song,B.,Zhang,N.N.,Wang,S.J.,Du,J.K.(2010):ChangesoftheHailuogouglacier,Mt.Gongga,China,againstthebackgroundofclimatechangesincetheHolocene.QuaternaryInternational,218(2010):166–175.(ReproducedwithPermission) Supervisor’sForewordThisstudymainlyexplorestheresponseofclimatechangeinthecoldregionsofChinatotheglobalchangesagainstthebackgroundofthemonsoonclimate.Basedontheobservationdata,thispapersystemicallyresearchesthespatiotemporalcharacteristicsofclimateinSouthwesternChinainnearly50years,andrevealsthedrivingmechanismofclimatechange.Onthisbasis,thisstudyalsodelvesintotheresponseoftheglaciersystemtoclimatechanges.Themainfindingsinthisstudyareasfollows:(1)Throughanalysisoftherecordsoffieldobservationsandpreviousstudies,somechangesarefoundinSouthwesternChina,includingsharptemperaturerises,slightinterannualvariabilityoftheprecipitation,obviousextremeclimateevents,significantdecreaseinsunshinedurationandwindspeed.Meanwhile,acloserelationbetweenspatialvariationofclimateandelevationhasbeenconfirmed.TheresearchconstructsthetemporalandspatialpatternsofclimatechangeinSouthwesternChina,whichmakesupforthedeficiencyofresearchontheclimatechangeinthestudyregion,andprovidesascientificbasisfortheestablishmentofcountermeasuresaboutslowingdownandadaptingtoclimatechange.(2)AimingatthecomplexityanduncertaintyofclimatechangeinSouthwesternChina,thisstudysystemicallyexplorestheactionmechanismbetweenthelarge-scaleatmosphericcirculationsystem,thecomplicatedtopography,humanactivities,andregionalclimatechanges.Atthesametime,thisstudyrevealsthetemporalandspatialcorrelationmechanismbetweencirculationsystemsandtheregionalclimatechanges,confirmsthesignificantinfluenceofthemicro-climateeffectcausedbythetopographychangetotheregionalclimatechange,andevaluatestheeffectsofhumanactivitiestoclimatechange,especiallythefasturbanizationprocess.Theseresultsprovideimportantinformationforaccurateassessmentonwarmingclimateandpredictionsofclimatechange,andprovideafavorablebasisforaprecipitationinfloodseasonandaforecastofextremeweather.Inaddition,theyimprovethelevelofresearchonclimatechangeinthecoldregionsofChina,enrichinganddevelopingthescientificvii viiiSupervisor’sForewordtheoryofglobalclimatechange.In2012,theresultswerepublishedinamagazinecalled“GlobalandPlanetaryChange”.Itisparticularlypleasingthattheresultsattractedconsiderableattentioncomparedwithothersofthesamescope,andwereincludedinESIin2013.(3)OnthebasisoftheanalysesofobservationdataonglaciersinSouthwesternChina,thisstudyanalyzestheresponseofglacierstoclimatechangefromthreeaspects(themorphologyoftheglacier,glacialmassbalance,andtheprocessofhydrology)sothatononehand,itisclearabouttherespondingrelationshipbetweenglaciermorphologicchangessuchasarea,lengthandicesurfacemicrorelief,andclimatechanges;andontheotherhand,themechanismoftheactionofclimatewarmingtobalancebetweenenergyandmatterisuncoveredinordertoillustratetheeffectsofaccelerationofglacialablationtoclimatechangeandinvestigatetheinfluenceofmeltwateronthehydrologicsystem.ThesefindingsshowtheresponseofglaciersinSouthwesternChinatoclimatechangeforthefirsttime,deepenandexpandthetheoreticalresearchofglacierresponse,whichcanprovidedecision-makingbasisfortheassessmentofmeltwaterchangeandthespecificcountermeasuresagainstthedisasterfromsnowandglaciersagainstthebackgroundofglobalwarming.ThisfindingwaspublishedinEnvironmentalResearchLettersin2011andreceivedextensiveconcernoftheinternationalacademia.TeppeiJ.Yasunari,aresearcherinNASAinvitedbytheperiodicaleditor,wroteareviewarticleentitled“WhatinfluencesclimateandglacierchangeinSouthwesternChina?”Likewise,thisfindingalsowasincludedinESIin2013.Intheory,theachievementsofthisstudyareimportanttoinnovationanddevelopment,whichhavemadeasignificantcontributiontoresearchontheresponseofclimateincoldregions,glaciers,andhumanactivitiestoaglobalchangeagainstthebackgroundofthetypicalmonsoonclimate,andhaveprovidedsomescientificbasesforpredictions,countermeasuresagainstdisastersduetoextremeweather,utilizationofwater,andtheestablishmentofcounterplanstoslowandadapttoclimatechange.WiththeintensifyingofChina’swesterndevelopment,itisbelievedthattheseresultswillplayamoreimportantroleinourcountry’ssustainabledevelopmentandecologicalconstructioninSouthwesternChina.Lanzhou,June2014Prof.YuanqingHe AbstractSouthwesternChinaincludestheSichuan,Yunnan,andGuizhouProvinces,theXizangAutonomousRegion,andChongqingMunicipality,withanareaof622.333×10kmaccountingfor24.5%ofthetotallandareaofChina.Thetopographydeclinesfromwesttoeastandfromnorthtosouth.Therearefourgeomorphicunits:theXizangPlateau,theHengduanMountains,theSichuanbasin,andtheYunnan–Guizhouplateau.SouthwesternChinaisatypicalmonsoonalclimateregion,controlledbytheSouthAsiamonsoonbutalsoinfluencedbytheEastAsiamonsoon.Inaddition,itisinfluencedbytheXizanganPlateaumonsoonandthewesterlies.AccordingtotheChineseGlacierInventory,2therewere23,221glaciersinsouthwesternChina,coveringanareaof29,523km,whichis50.16%ofthetotalglaciernumberand49.69%ofthetotalglacierareainChina.Climateresearchhasconcentratedmainlyonsub-regionsorsingledistrictsoverthestudyregion,however,therehasbeenlittlesystematicanalysisofclimatechangeinthewholeregion.Here,thetemporal-spatialvariationanditscausesofclimatechangeandtheglaciers’responseinsouthwesternChinaduring1961–2008havebeenanalyzedbasedonmeteorologicaldatafrom110stations,NCEP/NCARreanalysisdata,andtherecordsofglacierchangesfromfieldobservationsandpreviousstudies.Themainconclusionsofthepaperareasfollows:(1)AnnualandseasonalwarmingtrendsinsouthwesternChinaduring1961–2008weresignificant.About77%ofthe110stationsdisplayedstatisticallysig-nificantincreasesinannualtemperature.Theincreasewasmoreapparentinhigheraltitudeareasthaninlowerones.Warm–dryflowinsummeraffectedthestudyregion,andthesouthernextentofthewintermonsoonhasalsobeenweakened,whichinpartaccountsforsomeoftheclimatewarmingexperi-enced,especiallyinthewarmestyearsinsouthwesternChina.SunshinehourshaveacrucialinfluenceontheSBtemperature,especiallyduringspringandsummer,whereasthisinfluencemainlyiseffectiveinwinterattheXizangPlateau-HengdunaMountainsandYunnan-GuizhouPlateau.Inaddition,theincreasednetlongwaveradiationfluxovermostareasinthestudyregionandix xAbstractseasurfacetemperatureinWesternPacificmayhavealsomadesomecontri-butionstotemperaturerise.Precipitationvariationswerelessmarkedthanthoseoftemperature,generallyshowingweakdecreasingtrendsduring1961–2008.About53%ofthestationsexperiencedatrendofincreasingannualprecipi-tation.Stationswithprecipitationincreaseswerealsomainlyathigheraltitudesmainlyowingtothemorewatervaporflux,butthesignificancelevelwaslow.Northwardpenetrationofthesummermonsoonislimitedbyanincreasingnortheasterlyairflowovertheregion,andnorthwesterlywindsinthenorthpreventsouthwardtransportationofwatervaporfromtheoceaninsummer.Inaddition,thewatervaporfluxshowedweakvariationfromthemostprecipi-tationyearstotheleastyears.Thesecharacteristicssuggestaweakenedmon-soonalflowandvaportransportationinrecentyears,andalsopartlyexplaintheinconspicuousprecipitationvariationsoversouthwesternChina.Inaddition,thestrengtheningWesternPacificSubtropicalHighalsohashadsomeinfluenceonprecipitationvariations.(2)Analysisofchangesin12indicesofextremetemperatureand11ofextremeprecipitationat110meteorologicalstationsinsouthwesternChinaduring1961–2008revealedstatisticallysignificantincreasesinthetemperatureofthewarmestandcoldestnights,inthefrequenciesofextremewarmdaysandnights,andinthegrowingseasonlength.Decreasesinthediurnaltemperaturerangeandthenumberoffrostdayswerestatisticallysignificant,butadecreasingtrendoficedayswasnotsignificant.Inalargeproportionofthestations,patternsoftemperatureextremeswereconsistentwithwarmingsince1961.Warmingtrendsinminimumtemperatureindicesweregreaterthanthoserelatingtomaximumtemperature.WarmingmagnitudesweregreaterontheXizangPlateauandtheHengduanMountainsthanontheYunnan-GuizhouplateauandintheSichuanbasin,asconfirmedbythedecreaseoftheregionaltrendfromwesttoeast.Changesinprecipitationextremeswererelativelysmall,andonlytheregionaltrendsinconsecutivewetdays,extremelywetdayprecipitation,andmaximum1-dayprecipitationweresignificant.Thesetrendsaredifficulttodetectagainstthelargerinterannualanddecadal-scalevariabilityofprecipitation.Onthewhole,thenumberofrainydaysincreasedontheXizangPlateauandintheHengduanMountains,buttherainystrengthhasalsoincreasedatloweraltitudeareas.Analysisoflarge-scaleatmosphericcircula-tionchangesrevealsthatastrengtheninganticycloniccirculation,increasinggeopotentialheight,weakeningmonsoonalflow,andvaportransportationovertheEurasiancontinenthavecontributedtothechangesinclimateextremesinsouthwesternChina.ThespatialdistributionoftemporalchangesofallclimateextremeindicesinsouthwesternChinareflectstheobviousaltitudedependence.Trendmagnitudesoftemperatureextremesaresignificantlyhigherforflatstations,followedbysummit,intermountainbasin,andvalleystations.Itisobviousthatthelargerdecreasingtrendisinsummitstation,followedbyflat Abstractxistations,whereasthegreaterincreasingtrendmainlyoccurredinvalleystationsinsouthwesternChina,andtheintermountainstationsalsoshowedlowerdecreaseorincrease.Inaddition,themeancontributionoftheUHIeffectonregionaltrendsofurbanstationsforcoldextremesandwarmextremeswere16.0%and7.9%,respectively,basedonthepreliminaryevaluation.(3)Sunshine-hoursisoneofthemostimportantfactorsaffectingclimateandenvironment.TrendsoftemporalandspatialpatternsinsunshinehoursandassociatedclimaticfactorsoversouthwesternChinaareevaluatedfortheperiod1961–2008basedondatafrom110meteorologicalstations.TheresultsshowthatsouthwesternChinaisexperiencingstatisticallydecreasingsunshinehourswitharateof31.9h/10aduring1961–2008,andthestatisticallysignificantdecreaseinsunshinehoursmainlyoccurredinloweraltituderegions,especiallyinSichuanbasinandGuizhouplateau.Itshowedtheclosetemporalandspatialcorrelationbetweenwindspeedandsunshinehours,andthelargerdecreasingtrenddisplayeddecliningtrendonnon-windydaysthanthatonwindydays.Thisisstronglysuggestiveofthefactthatstrongerwindsleadtolongersun-shinehours,furthervalidatingthatwindspeeddirectlyandstronglyinfluencessunshinehoursinsouthwesternChina.Therelativehumidityalsohasgreatinfluenceonsunshinehoursreflectedbythesignificantcorrelationandthesimilartrendbetweenthetwovariables.Sunshinehoursalsohavehighcor-relationwithprecipitationandsurfacedownwardssolarradiationflux,whereastheeffectfromurbanizationonregional-scalestrendwasinconspicuous.Theincreasedtotalcloudcoverandcloudwatercontentfromthe1960sto1970s,andthedecreasedrelativehumidityandincreasedsurfacedownwardssolarradiationfluxbetweenthe1980sand1990shavealsoinfluencedthevariationinsunshinehours.Inaddition,theclearlocalinfluenceoftopographycanbereflectedbythedecreasingmagnitudesincreasedfromsummittoflatstations.(4)Dailywindspeeddatafrom110stationsinsouthwesternChinawereanalyzedtodeterminetrends,spatialdifferences,andpossiblecauses.Therewasasta-tisticallysignificantdecreaseof0.24m/s/10aintheannualmeanwindspeedduringtheperiod1969–2008.Thedecreasingtrendwasfaster(0.37m/s/10a)during1969–2000.Between2001and2008,therewasasignificantincrease.Thepatternofseasonalchangeswassimilar.Stationswithstronger,significantdecreasingtrendsweremainlyontheXizangPlateau,theHengduanMoun-tains,andtheYunnanPlateau,andstationswithsignificantincreasingtrendsweremainlyintheSichuanbasin,indicatingtheinfluenceofaltitudeonwindspeed.SurfacewindspeedsinsouthwesternChinahavebeenaffectedinrecentyearsbyboththechangedlarge-scaleatmosphericcirculationandtheregionalandglobalwarming.Theanalysishasconfirmedthatthedecreasingwindspeedduring1969–2000wascausedmainlybythedecreasingmonsoonalcirculationandWesterlies,andthestrengtheninglatitudinalwindspeedhasmadesomecontributionstotheincreasingwindspeedafter2000.Andwhatismore,the xiiAbstractstrengtheningXizanganmonsoonhasalsomadesomecontributionstowindchange,whichindicateslowerwindspeedswererelatedtoincreasedtemper-atures,particularlytoariseintheminimumtemperatureinrecentyears.Theweakwindspeedmayalsobecausedbytheasymmetricdecreasinglatitudinalgradientsofsurfacetemperatureandpressuregradientduring1969–2008.Thedataindicatedapositivecorrelationbetweenwindspeedandsunshinehourssuggestinganotherpossibleinfluencingfactor.Topographicalinfluencesareevidentinthehigherannualandseasonaltrendsatsummitandintermontanebasinstationsandthelowertrendsatvalleystations.Inaddition,aminorinfluencefromurbaneffectonwindspeedhasalsobeenfound.(5)GlaciersaredistributedinNyainqntanglhaMountains,Himalayas,TanggulaMountains,GangdiseMountains,andHengduanMountainsinsouthwesternChina.Undertemperaturerise,especiallytheincreasingwarmingwithaltituderecordedby110stations,icecores,andtreeringsinsouthwesternChina,fourcharacteristicsofglaciervariationsoccurredduringtherecentdecades:thefrontsof32glaciersandareasof13glacialbasinshaveretreated,masslossesoftenglaciershavebeenconsiderable,glaciallakesinsixregionshaveexpandedandmeltwaterdischargeoffourbasinshasalsoincreased;thetypicalglaciershowstheaccelerativeablation.TheremarkableregionaldifferencesinglacierchangeinsouthwesternChinamaybecausedbythefollowingtwofactors:differencesintemperatureandprecipitation;anddifferencesinglacierlocation,scale,andfrontalaltitude.Asresponsetoclimatechange,eightmonsoonaltemperateglacierswereinstationaryoradvancingbetweenthe1900s–1930sandthe1960s–1980s,andwereinretreatfromthe1930stothe1960sandfromthe1980stothepresent.Inotherwords,itisevidentthattheglacierretreatstagesareinthewarmandwetphases,andviceversa.TheaccumulatedmassbalanceinHailuogoubasinis−10.83mwaterequivalentinthepast45years,anannualmeanvalueof−0.24mwaterequivalent,and29yearsarenegativemassbalanceyear,showingthatitsufferedasustainedmasslossofsnowandiceintheperiod1959/1960–2003/2004.Andwhatismore,thewarmingcli-matehashadanimpactonthehydrologicalcycleatglacialarea.Astheglacierareasubjecttomeltinghasincreasedandtheablationseasonhasbecomelonger,thecontributionofmeltwatertoannualriverdischargehasincreased,whichcanbereflectedbytheincreasedrunoffinthedownstreamregionoftheglacialareaoftheYanggongjiangbasinduring1979–2003andHailuogoubasinduring1999–2004,andthemeancontributionoftherunoffinthedownstreamregionoftheglacialareatothewholebasinare35.8%and54.7%,respectively.Theearlieronsetofablationathigherelevationglaciershasresultedintheperiodofminimumdischargeoccurringearlierintheyear,andseasonalrunoffvariationsaredominatedbysnowandglaciermelt.Theincreasedamplitudeofrunoffinthedownstreamregionoftheglacialareaismuchstrongerthanthatofprecipitation,resultingfromtheprominentincrease Abstractxiiiofmeltwaterfromglacialregionintwobasins.Astheaccelerationofablationvelocity,thelengtheningofablationperiodandtheextensionofablationarea,changesofinternalanduppersurfacemorphologyalsooccurredcharacterizedbymanyice-clefts,glaciercollapses,decreaseinthickness,enlargementofglacialcaves,andreductioninthesizeofseracs,providingevidenceoftheresponsetoclimaticwarminginrecentyears.However,itisdifficulttodiscussthequantitativerelationshipbetweenclimatechangeandglacierbehaviorinsouthwesternChinaowingtothelimitedobservationintheglacialaccumulationareasandthecomplexityofclimatechangeandglacierdynamicresponse.KeywordsClimatechange
Glaciers
SouthwesternChina AcknowledgmentsFirstandforemost,Iwouldliketoexpressmygratitudetoallthosewhosehelpedmeduringthewritingofthethesis.Igratefullyacknowledgethehelpofmysupervisor,Prof.YuanqingHe,whohasofferedmevaluablesuggestionsintheacademicstudies.Inthepreparationofthethesis,hehasspentmuchtimereadingthrougheachdraftandprovidedmewithinspiringadvice.Withouthispatientinstruction,insightfulcriticism,andexpertguidancethecompletionofthisthesiswouldnothavebeenpossible.Second,IalsooweaspecialdebtofgratitudetoalltheprofessorsinColdandAridRegionEnvironmentandEngineeringResearchInstitute,ChineseAcademyofSciences,fromwhosedevotedteachingandenlighteninglecturesIhavebenefitedalotandacademicallypreparedforthethesis.AnyprogressthatIhavemadeistheresultoftheirprofoundconcernandselflessdevotion.Amongthemthefollowingrequiremention:ResearcherFengQi,ResearcherLiZhongqin,ResearcherZhangYaonan,ResearcherHouShugui,Prof.WilfredH.Theakstone(UniversityofManchester),Prof.NormCatto(MemorialUniversityofCanada),ResearcherRenJiawen,ResearcherWangNinglian,ResearcherZhangDian,ResearcherKangShichang,ResearcherLiuGuangxiu,ResearcherZhangJingguang,ResearcherQuJianjun,ResearcherXiaoHonglang,ResearcherDuanKeqin,Prof.ZhangZhibin,Prof.ZhangMingjun,ResearcherYangMeijue,ResearcherTianLide,ResearcherLuAnxin,ResearcherChenTuo,ResearcherLiuShiyin,ResearcherLiShuxun,ResearcherPuJianchen,AssociateprofessorLiuXunwang,AssociateprofessorJiaoKeqin,AssociateprofessorLiuXiaohong,AssociateprofessorLiYuefang,andAssociateprofessorJingZhefan.Third,Ishouldliketoexpressmygratitudetomybelovedfamily,whichhasalwayshelpedmeoutofdifficultiesandsupportedmewithoutawordofcomplaint.Ialsoowemysinceregratitudetomyfriendsandmyfellowclassmateswhogavemetheirhelpandtimeinlisteningtomeandhelpingmeworkoutmyproblemsduringthedifficultcourseofthethesis.Amongthemthefollowingrequiremention:Prof.ZhangZhonglin,Prof.LuAigang,AssociateprofessorJiaWenxiong,AssociateprofessorPangHongxi,AssociateprofessorZhaoJingdong,AssociateprofessorYuanLingling,AssociateresearcherNingBaoying,Dr.SongBo,Dr.Guxv xviAcknowledgmentsJuan,Dr.ZhangNingning,Dr.WangShijin,Dr.HeXianzhong,Dr.ZhangWei,Dr.CaoWeihong,Dr.ChangLi,Dr.WangShuxin,Dr.ZhuGuofeng,Dr.DuJiankuo,Dr.XinHuijuan,Dr.PuTao,WangChunfeng,ZhangTao,LiuJing,HeZhi,ChenShifu,ChenYupeng,HeLihua,ZhouXiaolan,ZhangWenjing,etc.Last,mythanksareowedtosomeorganizationswhichprovidedsubsidiestothisthesis.ThisstudywassupportedbytheNationalNaturalScienceFoundationofChina(41201024),KeyLaboratoryofWesternChina’sEnvironmentalSystems(MinistryofEducation),WestLightProgramforTalentCultivationofChineseAcademyofSciences,theKeyProjectofChineseAcademyofSciences(KZZD-EW-04-05),theChinaPostdoctoralScienceFoundationFundedProject(2012M510219,2013T60899),theYouthInnovationPromotionAssociation,CAS,theimportantprojectofChineseAcademyofSciences(KZCXZ-YW-317),thekeyprojectofChinamechanicalvirtualhuman(90511007,91025002,40725001),thetrainingprogramofGlaciologyandGeocryology(J0630966,11J0930003),theindependentresearchprojectsofStateKeyLaboratoryofCryosphericSciencesandtheentrustedprojectofLijiangCity. Contents1Introduction........................................11.1BackgroundandSignificanceofTopics.................11.2AdvancesinClimateChangeResearch.................101.2.1TheFactofClimateChange...................101.2.2TheMechanismofClimateChange..............171.2.3TheImpactofClimateChange.................201.2.4TheCurrentCharacteristicsoftheClimateChangeResearch..........................231.3TheMainContents...............................25References..........................................262DataandMethods...................................372.1Data.........................................372.1.1TheObservationData.......................372.1.2TheDataonGlacierChange..................442.1.3TheReanalyzedData.......................462.2Methods......................................472.2.1TheLinearTrend..........................472.2.2MovingMean............................482.2.3TheCalculationofRegionalTrend..............482.2.4TheDefinitionofUrbanStationandRuralStationandtheBasisofClassification............492.2.5TheDivisionofSub-regions...................502.2.6TheChangesofAtmosphericCirculationSysteminaLargeScale...........................502.2.7TheDefinitionandCalculationofExtremeEventIndex..............................52xvii xviiiContents2.2.8TheCalculationofGlacierLengthandMaterialBalance.................................552.2.9TheCalculationofWaterOutputinSnowandIceatHighAltitudes.....................56References..........................................573SpatialandTemporalVariationofTemperatureandPrecipitationinSouthwesternChina...................613.1TemporalVariationofTemperatureandPrecipitation.......613.1.1MeanTemperatureandPrecipitation.............613.1.2TheAnnualChangeofTemperature.............643.1.3TheAnnualPrecipitationVariation..............663.1.4Inter-annualVariationofTemperatureandPrecipitationinMonsoonPeriodandNonMonsoonPeriod....................683.1.5TheTemperatureandPrecipitationVariationReflectedbyIceCoresandTreeRings...........713.2SpatialVariationofTemperatureandPrecipitation.........743.2.1TheSpatialDistributionofTemperatureVariation...743.2.2TheSpatialDistributionofPrecipitationVariation...753.2.3TheSpatialDistributionofTemperatureandPrecipitationVariationinSummerMonsoonPeriodandWinterMonsoonPeriod.......773.3DrivingMechanismforTemperatureandPrecipitation.......793.3.1TheRelationshipofTemperatureandPrecipitationVariationwithElevation.....................793.3.2TheCorrelationwithTemperatureVariation,Radiation,SeaSurfaceTemperatureandSunshineHours..................................843.3.3TheCorrelationofTemperatureandPrecipitationVariationandAtmosphericCirculation...........873.3.4TheComparisonofVariationMagnitudeofTemperatureinUrbanandRuralStations........943.4Summary......................................97References..........................................994SpatialandTemporalVariationofClimateExtremesinSouthwesternChina................................1014.1SpatialandTemporalVariationofClimateExtremes........1014.1.1SpatialandTemporalVariationofIndicesofTemperatureExtremes.....................1014.1.2SpatialandTemporalVariationsofPrecipitationExtremes................................106 Contentsxix4.2ComparisonAmongClimateExtremesIndexes............1114.2.1TheConsistencyofClimateExtremesIndexes......1114.2.2TheRegionalDifferenceofClimateExtremesIndexes.................................1154.2.3TheComparisonofColdnessandWarmthIndexes...1174.2.4TheComparisonofThisStudyandOtherSources...1194.3DrivingMechanismforClimateExtremes...............1194.3.1TheCorrelationwithClimateExtremesandAtmosphericCirculation..................1194.3.2TheCorrelationwithClimateExtremesandElevation.............................1254.3.3TheComparisonofTemperatureExtremesBetweenUrbanandRuralStation...............1314.4Summary......................................133References..........................................1345SpatialandTemporalVariationofSunshineHoursinSouthwesternChina................................1375.1TemporalVariationofSunshineHours.................1375.1.1MeanSunshineHours.......................1375.1.2TheInterannualVariationofSunshineHours.......1395.2SpatialVariationofSunshineHours...................1445.2.1SpatialDistributionofVariationTrendsinSunshineHoursDuring1961–2008............1445.2.2SpatialDistributionofVariationTrendsinSunshineHoursBetween1961–1990and1991–2008............................1465.3DrivingMechanismforSunshineHours................1505.3.1RelationshipBetweenWindSpeedandSunshineHours........................1505.3.2TheRelationshipBetweenRelativeHumidityandSunshineHour.........................1535.3.3TheComparisonofSunshineHoursBetweenUrbanandRuralStations.....................1555.3.4CorrelationwithSunshineHourandOtherMeteorologicalFactors......................1615.3.5CorrelationwithSunshineHourandAltitude.......1635.4Summary......................................165References..........................................167 xxContents6SpatialandTemporalVariationofWindSpeedinSouthwesternChina................................1696.1TemporalVariationofWindSpeed....................1696.1.1TheMeanWindSpeed......................1696.1.2TheInterannualVariationofWindSpeed.........1716.2SpatialVariationofWindSpeed......................1746.2.1TheSpatialDistributionoftheWindSpeedVariationBetween1969–2008and1969–2000......1746.2.2SpatialDistributionofWindSpeedVariation.......1786.3DrivingMechanismforWindSpeed...................1806.3.1CorrelationwithWindSpeedandLarge-ScaleAtmosphericCirculation.....................1806.3.2CorrelationwithWindSpeedandRegionalWarming................................1866.3.3CorrelationwithWindSpeedandSunshineHour....1906.3.4CorrelationwithWindSpeedandAltitude.........1916.3.5ComparisonofWindSpeedBetweenUrbanandRuralStations..........................1926.4Summary......................................194References..........................................1967GlaciersResponsetoClimateChangeinSouthwesternChina....1997.1CharacteristicsofGlaciersChange....................1997.1.1TheGlacierRetreatandShrinkingAreas..........1997.1.2SevereMassLossofGlacier..................2027.1.3ExpansionofIceLakesorLakesSuppliedbyIces...2037.1.4TheSignificantGlacierMelt..................2057.2ShorteningofGlaciersLength.......................2067.2.1CharacteristicsofStageinGlaciersLength........2067.2.2TheSpatialDifferenceofGlacierRetreat..........2077.2.3TheRelationshipofGlacierLengthandClimateChange.................................2087.3NegativeBalanceofGlacierMass.....................2127.3.1BalanceofGlacierMassinHailuogouGlacier......2127.3.2TheRelationshipBetweenMassBalanceChangesinHailuogouGlacierandClimateChanges................................2137.4IncreasingofGlacialRunoff........................2157.4.1ProcessofRunoffChangesinYanggongRiver.....2157.4.2ProcessofRunoffChangeinHailuogou..........2197.4.3PossibaleEffectsofIncreasingDischargeatHighAltitude...........................221 Contentsxxi7.5FragmentationofGlacierMicrotopography..............2227.5.1SurfaceMorphologyChangeofBaishuiNo.1......2227.5.2SurfaceMorphologyChangeofHailuogouGlacier...2247.5.3TheChangesofGongbaGlacier................2257.5.4TheResponseofGlacierSurfaceMorphologyChangestoClimateChange...................2267.6Summary......................................227References..........................................2298TheMainConclusionandProspect.......................2338.1Conclusions....................................2338.2Prospect.......................................239References..........................................242 ZongxingLi’sResumeInstituteColdandAridRegionEnvironmentandEngineeringResearchInstitute,ChineseAcademyofSciencesAddressNo.320,TheWestDonggangRoad,ColdandAridRegionEnvironmentandEngineeringResearchInstitute,ChengguanDistrict,Lanzhou,China,730000Mobile86-13919887317Emaillizxhhs@163.comDateofBirthMarch1984BirthplaceHuining,GansuProvinceDegree/TitleofPh.D./AssistantProfessoratechnicalpostEducationGraduatePoliticsstatusPartymemberMajorPhysicalGeographyResearchClimatechangeandhydrologyresponsedirectionEducationBackground2002.9–2006.7DepartmentofGeographyinCollegeofGeographyandEnvironmentalScience,NorthwestNormalUniversity,Bach-elorDegree2006.9–2009.7Majoredinclimatechangeandglacierresponse,ColdandAridRegionEnvironmentandEngineering,ChineseAcademyofSciences,PhysicalGeographyMasterDegree2009.7–2012.1Majoredinclimatechangeandcoldregionhydrology,ColdandAridRegionEnvironmentandEngineering,ChineseAcademyofSciences,PhysicalGeographyDoctorDegreexxiii xxivZongxingLi’sResumeEmployingExperiences2012.1–presentAssistantResearchFellow,specializedinclimatechangeandcoldregionhydrology,ColdandAridRegionEnvironmentandEngineering,ChineseAcademyofSciencesScientificResearchProjects1.2013.1–2015.12,ProjectforNationalNaturalScienceFoundationofChina:StudyonhydrographseparationusingstableisotopesandchemicalionsforglacialwatershedatQilianMountainsduringablationperiod(41201024),260,000RMB,projectdirector;2.2014.1–2016.12,ProjectforWestLightFoundationofTheChineseAcademyofSciences:StudyonquantifyinginternalrecyclemoisturefractioninprecipitationattheeasternQilianmountainsandHexicorridor,200,000RMB,projectdirector;3.2012.6–2014.6,ProjectforChinaPostdoctoralScienceFoundation:HydrographseparationinglacialwatershedatQilianMountains(No.2012M510219),80,000RMB,projectdirector;4.2013.6–2015.6,ProjectforSpecialGrantforChinaPostdoctoralScienceFoundation:Contributionfrominternalrecyclemoisturefractiononprecipita-tioninShiyangriverbasin(No.2013T60899),150,000RMB,projectdirector;5.2013.1–2016.12,ProjectfortheYouthInnovationPromotionAssociationofChineseAcademyofSciences:StudyonIsotopehydrologyfordifferentcoldbasinsinQilianmountains,400,000RMB,projectdirector;6.2009.1–2010.12,ProjectforCASSpecialGrantforPostgraduateResearch,InnovationandPractice:StudyonGlacierschangeinHengduanMountains,20,000RMB,projectdirector;7.2009.1–2010.12,ProjectforIncubationofSpecialistsinGlaciologyandGeo-cryologyofNationalNaturalScienceFoundationofChina(J0630966):studyonResponseofRunoffinHighAltitudeAreaovertheTypicalChineseMonsoonalTemperateGlacialRegiontoClimateWarming,40,000RMB,projectdirector;8.2010.1–2011.12,ProjectforIncubationofSpecialistsinGlaciologyandGeo-cryologyoftheNationalNaturalScienceFoundationofChina(11J0930003):studyonclimatechangeandglaciersresponseinSouthwesternChina,40,000RMB,projectdirector. ZongxingLi’sResumexxvPublicationsPublishedinInternationalJournals1.ZongxingLietal.SpatialandtemporaltrendofpotentialevapotranspirationandrelateddrivingforcesinSouthwesternChina,during1961–2009.Qua-ternaryInternational,2013,doi:10.1016/j.quaint.2013.12.045.2.ZongxingLietal.ChangesofdailyclimateextremesinSouthwesternChinaduring1961–2008.GlobalandPlanetaryChange,80–81(2012):255–272.3.ZongxingLietal.ClimateandglacierchangeinSouthwesternChinaduringthepastseveraldecades.EnvironmentalResearchLetters,6(2011)04540.4.ZongxingLietal.DecreasingtrendofsunshinehoursandrelateddrivingforcesinSouthwesternChina.TheoreticalandAppliedClimatology,2012,109(2012):305–321.5.ZongxingLietal.AltitudedependencyoftrendsofdailyclimateextremesinSouthwesternChina,1961–2008.JournalofGeographicalSciences,2012,doi:10.1007/s11442-011-0000-0.6.YangXiaomei,ZongxingLi(correpondingauthor)etal.ThedecreasingwindspeedinSouthwesternChinaduring1969–2009,andpossiblecauses.Qua-ternaryInternational,2012,263(2012):71–84.7.PangHongxi,ZongxingLi,TheakstoneW.H.ChangesofthehydrologicalcycleintwotypicalChinesemonsoonaltemperateglacierbasins:aresponsetoglobalwarming?JournalofGeographicalSciences,2012,22(5):771–780.8.ZongxingLietal.Spatialandtemporaltrendsoftemperatureandprecipitationduring1960–2008attheHengduanMountains,China.QuaternaryInterna-tional,236(2011):127–142.9.ZongxingLietal.Changesofclimate,glaciersandrunoffinChina’smon-soonaltemperateglacierregionduringthelastseveraldecades.QuaternaryInternational,2010,218(2010):13–28.10.ZongxingLietal.ChangesoftheHailuogouglacier,Mt.Gongga,China,againstthebackgroundofclimatechangesincetheHolocene.QuaternaryInternational,2010,218(2010):166–175.11.ZongxingLietal.EnvironmentalSignificanceofSnowpitChemistryintheTypicalMonsoonalTemperateGlacierRegion,BaishuiGlacierNo.1,Mt.Yulong,China.EnvironmentalGeology,2009,58:1319–1328.12.ZongxingLietal.ThechemistryofsnowdepositedduringthesummermonsoonandinthewinterseasonatBaishuiNo.1Glacier,Mt.Yulong,China.JournalofGlaciology,2009,55(190):221–228.13.ZongxingLietal.Environmentalsignificanceofsnowpitchemistryinthetypicalmonsoonaltemperateglacierregion,BaishuiglacierNo.1,Mt.Yulong,China.EnvironmentalGeology,58(2009):1319–1328.14.ZongxingLietal.SourceofmajoranionsandcationsofsnowpacksinHail-uogouNo.1glacier,Mt.GonggaandBaishuiglacierNo.1,Mt.Yulong,China.JournalofGeographicalSciences,2008,14(1):115–125. xxviZongxingLi’sResume15.YuanqingHe,TaoPu,ZongxingLietal.ClimatechangeanditseffectonannualrunoffinLijiangBasin-Mt.YulongRegion,China.JournalofEarthScience,2010,21(2):137–147.16.LuAigang,ShichangKang,ZongxingLietal.AltitudeeffectsofclimaticvariationonTibetanPlateauanditsvicinities.JournalofEarthScience,2010,21(2):189–198.17.PangHongxi,YuanqingHe,NingningZhang,ZongxingLi.Observedgla-ciohydrologicalchangesinChina’stypicalmonsoonaltemperate-glacierregionsincethe1980s.China.JournalofEarthScience,2010,21(2):179–188.18.HeXianzhong,DuJiankuo,JiYapengZhangNingning,ZongxingLi,WangShijin.CharacteristicsofDDFattheBaishuiglacierNo.1RegioninMt.Yu-long.China.JournalofEarthScience,2010,21(2):148–156.19.ZongxingLietal.Studyonthecontributionfromcryospheretorunoffinacoldalpinebasin:acasestudyfromHulugoubasin,themiddleQilianMountains.2014(underreview)20.ZongxingLietal.EnvironmentalsignificanceandhydrochemicalprocessesatacoldalpinebasinintheQilianMountains.2014(underreview)21.ZongxingLietal.CanmonsoonmoisturearriveQilianmountainsinsummer?2014(underreview)22.ZongxingLietal.CompositionofwetdepositioninthecentralQilianMountains,China.2014(underreview)PublishedinChineseJournals23.ZongxingLietal.ResponseofrunoffinhighaltitudeareaoverthetypicalChinesemonsoonaltemperateglacialregiontoclimatewarming.EarthSci-ence-JournalofChinaUniversityofGeosciences,2010,35(1):43–49.24.ZongxingLietal.Rainwaterchemistryanditsenvironmentalsignificanceinatypicalmonsooonaltemperateglacialregion,China.ScientiaGeographicaSinica.2010,30(4):588–593.25.ZongxingLietal.ChangesofsomemonsoonaltemperateglaciersinHengduanmountainsregionduring1900–2007.ActaGeographicaSinica,2009,64(11):1319–1330.26.ZongxingLietal.Rainwaterchemistryanditsenvironmentalsignificanceinatypicalmonsooonaltemperateglacialregion,China.ScientiaGeographicaSinica,2010,30(4):588–593.27.ZongxingLietal.Analysisonchemicalcompositionsofrainwaterinsummer,LijiangCity,China.EnvironmentalScience,2009,30(2):362–367.28.ZongxingLietal.ChangesinHailuogouduringtherecent100yearsunderglobalwarming.JournalGlaciologyandGeocryology,2009,31(1):75–81.29.ZongxingLietal.EnvironmentalrecordsfromashallowProfile,BaishuiNo.1Glacier,Mt.Yulong.EarthandEnvironment,2009,37(4):360–365.30.ZongxingLietal.ChemicalcharacteristicsonmajorionsofrainwaterinLijiangCity.EnvironmentalChemistry,2008,27(5):648–652. ZongxingLi’sResumexxvii31.ZongxingLietal.EnvironmentalrecordofsnowpackchemistryintypicalChinesemonsoonaltemperateglacierregion.ScientiaGeographicaSnica,2009,29(5):703–708.32.ZongxingLietal.Variationofclimate,glaciersandrunoffovermonsoonaltemperateglacialareainrecent100years,China.JournalofLanzhouuni-versity(naturalsciences),2008,44:1–5.33.ZongxingLietal.Responseof“glaciers-runoff”systeminatypicaltemperate-glacier,HailuogouglacierinGonggaMountainofChinatoglobalchange.ScientiaGeographicaSnica,2008,28(2):229–234.HonorsandAwards(onlyinpostgraduatestage)OutstandingpostdoctorofColdandAridRegionEnvironmentandEngineeringResearchInstitute,ChineseAcademyofSciences,2013;OutstandingdoctoraldissertationsofChineseAcademyofSciences,2013;OutstandinggraduatesofGraduateUniversityofChineseAcademyofSciences,2012;ChineseAcademyofScience(CAS)presidentspecialaward,2012;TheBHPBScholarshipofGraduateUniversityofChineseAcademyofSciences,2011;ExcellentLeaguememberofChineseAcademyofSciences,2011;YoungResearcherNewStarScientistAwardinthe“2010SCOPUSYoungResearcherAwardSchemeforClimateChange”,2010;The“LuJiaxiScholarshipforExcellentdoctoralstudent”,2010;The“ZhuLiYueHuaScholarshipforExcellentdoctoralstudent”,2010;TheTri-excellentstudentofChineseAcademyofScience,2010;Second-ClassofPhysicalSciencePrizeinGansuProvince,2009;TheChineseAcademyofScience(CAS)presidentawardofexcellence”,2009;The“LiuTungshengScholarshipforEarthSciences”,2009;Second-ClassScholarshipoftheThird“ORGANOPRIZE”,2009;Third-ClassScholarshipofthesecond“ORGANOPRIZE”,2008;“ExcellenceAward”paperinthedoctoralconsortium,2008.SocialServiceAsthereviewerforClimateDynamics,InternationalJournalofClimatology,QuaternaryInternational,JournalofEarthSciences,JournalofGeographicalsciences,MountainResearchandDevelopment,FreseniusEnvironmentalBulletin,ActaGeographicaSinicaandScientiaGeographicaSinica. Chapter1Introduction1.1BackgroundandSignificanceofTopics“ClimateChangeisnotonlyanenvironmentalissue,butalsoadevelopmentissue,inthefinalanalysisitisthedevelopmentproblem.”ClimateChangeResearch,ahotspotintoday’sinternationalscientificresearchfield,isrelatedtonationalsurvivalanddevelop-mentspace.Thus,athoroughstudyonclimatechangeinsouthwestChinaishelpfultohaveacomprehensiveunderstandingoftheprocessofthetheclimatechangeinthisregionandtheresponseoftheglobalchange.Itwillraisetheleveloftheclimatechangeresearchintheareaandprovideascientificbasisfortheestablishmentofcountermeasurestoslowandadapttoclimatechange.AccordingtotheIPCC’sfourthassessmentreport(2007),theobservedresultsincludingrisingglobalmeantemperaturesandSST,awiderangeoficeandsnowmelt,andtheglobalmeansealevelriseintherecenthundredofyears,etc.,showedthatthetendencyofclimatewarminghasbecomingmoreandmoreobvious.Itsconcretemanifestationarepresentedasfollow:(1)Inthelast100years,globalmeantemperaturesincreased0.74°C,andthereare11yearsintop12warmyearsbetween1995and2006.(2)Sealevelriseisechoedbythetrendsoftheclimatewarming.Theglobalmeanrateofsea-levelriseis1.8mm/a;since1993,themeanratehasincreasedto3.1mm/a.Reasonsofresultinginsuchstatusarecomplicated.Thereinto,thethermalexpansionandthemeltingofglacier,icecapandpolaricesheetsisdeepprimematter.(3)Thesnowandtheseeiceareasignificantlyreduced.Itisshowedbythesatellitedatathatsince1978,thearcticseaicesheetshasbeenshrinkingatarateof2.7%/10a.Indeed,theratesofretreatismoresignificant,7.4%/10a,andmountainglaciersandsnowcoverareaofboththeNorthernandSouthernhemispherealsoshowatrendofshrinking.(4)From1900to2005,theprecipitationintheeastareaofNorthandSouthAmerica,NorthernEurope,NorthernAsiaandCentralAsiaincreasedsignificantly,butinSahel,Mediterranean,SouthAfricaandpartsofSouthAsia,precipitationisreducingyearbyyear.It’sonthecardsthatsince1970s,theaffectedareaoftheglobalareahaveexpanded.(5)Overthepast50years,thefrequencyofcoldday,coldnightandfrostinthemostofthelandhadreduced.Whereas,warmdayandwarmnighthad©Springer-VerlagBerlinHeidelberg20151Z.Li,StudyonClimateChangeinSouthwesternChina,SpringerTheses,DOI10.1007/978-3-662-44742-0_1 21Introductionbecomemorefrequent,followedbymoresevereprecipitationevents,regionalfloods,andstrongstorm.(6)Theobserveddataconfirmedthatsincearound1970,tropicalcycloneactivityoftheNorthAtlantichasbeenincreasing.(7)Theobser-vationsofthelandandthemostofoceandemonstratethatalotofnaturalsystemsareaffectedbyregionalclimatechange,especiallytherisingtemperature.Alongwiththechangeofthesnow,glaciersandpermafrosts,thesizeandnumberofglaciersandlakescontinuetogoup,andtheinstabilityofthemountainandthepermafrostisincreasing,evensomechangesinecosystemsofbothNorthandSouthpoleemerge.Theobviousaugmentofriverrunoffappearedintheriverssuppliedbyglaciersandsnowandthepreactofmaximumflowinspringhavemadeanimpactonsomehydrologicalsystems.Inaddition,thewarmingofriversandlakesalsoaffecttheirthermalstructureandwaterquality.(8)Intheterrestrialecosystems,withtheearlierarrivalofspringevents,thegrowingrangeoftheplantsandtheanimalsgoestowardthepolesandhighaltitudearea.Thesechangesarerelatedtotherecentwarming.Similarly,insomemarineandfreshwatersystems,themigrationandchangesofbreedingrangesofthealgae,planktonandfisharerelatedtothewarmerwaterandtherelatedchangesoficecaps,oxygencontentandcirculation(IPCC2007).Moreover,inthe20thcentury,thetemperatureunder200–1,000mdeepascended0.5°C,andabout80%oftheboreholetemperatureisrising(Huangetal.1997;Pollacketal.1998).Accordingtotheanalysisofthesoundingdata,itwasfoundthatsince1958,thegeneralwarmingtrendoftheunderlyinglevelofthetropospherearenearlysimilartothatofthestrata,warmingapproximately0.1°C/10a(Gaffenetal.2000).Theresultsgotthroughthesatellitemicrowaveverifiedthatthewarmingtrendoftheunderlyinglevelintroposphereis0.05°C/10a(Brownetal.2000).Overhalfacentury,thetroposphericatmospherictemperatureinthesouthernhemisphereshowedatrendofgrowing,withtemperaturesrangerisingfromlowtohighgrad-ually.Thereinto,theheatingrateofthe1,000hPainthegroundflooris0.013°C/a,theheatingrateofthe500hPainthemiddleoftroposphereis0.019°C/a,thewarmingrateof300hpaintheuppertroposphereis0.036°C/a.Intherecenthundredofyears,asthemaincharacteristicsofclimatechanges,warminghavetakenplaceinmanysectionsofChina:(1)From1905to2001,China’sannualmeantemperatureappearedtobeontherise.Itincreasesby0.79°Cin1997;the1940sandafterthemiddleof1980saretwospecialperiods,inwhichthetemperatureobviouslyisontherise.(2)From1905to2001,thechangeinChina’smeanannualprecipitationisnotverysignificant.Itdecreasesby8.6mmin1997;moreprecipitationoccurinthe1910s,1930s–1940sand1980s–1990s,whereaslessprecipitationoccurinotherperiods(CountryAssessmentofClimateChanges2007).(3)Intherecent50years,thefrequencyandintensityofChina’smainextremeweatherandclimateeventsemergesignificantchanges,mainlyshowingastheworseningdroughtconditionsinnorthandnortheastofChinaandtheaggravatingfloodoverthemiddleandlowerreachesoftheYangtzeRiverandChina’ssoutheastarea.Since1990,theannualprecipitationismorethanordinaryyear,whichresultedin‘southernfloodandnortherndrought’andfrequentdroughtandflooddamage(CountryAssessmentofClimateChanges2007).(4)Duringtheperiodof1950s–1990s,themeanrateofsea-levelriseofchina’scoastalareais 1.1BackgroundandSignificanceofTopics32.5mm/a,whichishigherthattheglobalmeanfrom1993to2001,therateofsea-levelriseofYellowSeaandEastChinaSeais5–8.6mm/a,whichisslightlyhigherthantheglobalmean.Inthebook“TheEvolutionofChina’sClimateandEnvi-ronment”publishedin2005,itwasshowedthattherehaveexperienced19con-secutivewarmwintersinChinafrom1986/1987.Amongthem,thetemperaturein1951increasedsignificantly.Fromthechangeoftheprecipitation,althoughthenationalmeanprecipitationinnearly50yearsdidnotshowobvioustendency,therearesignificantregionaldifferences.TherainfallinthemiddleandlowerreachesoftheYangtzeriverandwestpartsofNorthwestChinaincreasedsignificantly.Onthecontrary,therainfallinthesoutheasternNortheastChina,NorthChinaandeasternpartsofNorthwestChinadecreasedsignificantly.Obviously,itmeansthatpre-cipitationintensityislikelytoincreasealongwiththereduceofprecipitationdaysalloverthecountry.Geetal.(2011)analyzetherateofthetemperaturevariationoverthepast2000yearsbythecomparisonofeveryhundredyearsandevery30yearsandthatofthepast500yearsbythecomparisonofevery10years.Theresultsindicatethatfromthenationalmean,theheatingrateis(0.6+1.6)°C/100aonthehundredscaleduringthe20thcentury;inthepast500years,themaximumheatingratehappenedintheheprocessoftransformationfromtheLittleIceAgetothewarmperiodof20thcenturyis(1.1+1.2)°C/100a,whichmaybethemax-imuminthepast2000years.Onthe30scale,althoughthenationalmeantem-peraturerisessignificantlyduringthe20thcentury,themaximumheatingrateisstilllessthanthatofthehistorictime,whichoccurredattheendofLittleIceAgeand270–320A.D.,respectively.Onthe10scale,thewarmingattheendofthe20thcenturyisveryobvious,butitisnotunprecedentedinthepast500years,anditstime,lengthandrangeexistregionaldifferences.Duringthe20thcentury,thefastesttemperaturereductionofthenationalmeanonthe10scaleoccurredin1940–1950,therateofwhichis(0.3+0.6)°C/10aandissimilartothat20thcenturyago.Themaximumcoolingrateofeachdistrictduringthe20thcenturydoesnotexceedthemaximumoneofhistoricalperiods.Underthebackgroundofglobalclimatechanges,whatchangeshavetheclimateofSouthwestChinaexpe-riencedinrecentyears?Whatarethecharacteristics?Whichfactorswillinfluenceit?Theinquiryofabovequestionswillbehelpfultohaveacomprehensiveunderstandingoftheprocessofregionalclimatechangeandtheresponseontheglobalchange,tofurtherimprovethearea’sclimatechangeresearch,toraisetheleveloftheclimatechangeresearchandtoprovidescientificbasisfortheestab-lishmentofcountermeasurestoadapttoandslowclimatechange.Glacieristhemaincomponentofthecryosphere,isthekeylinkofwatercycle,istheamplifierandindicatorofclimatechangeandistheimportantresourcetosupportregionaldevelopment.SosystemataciallyexploringtheresponsecharacteristicsofglaciertoclimatechangeinSouthwesternChinacontributestohaveacomprehensiveunderstandingoftheinfluenceofclimateontheglaciersystem,todeepenandextendthetheoreticalstudyoftheglacierresponse,andtoprovidetheoreticalbasisforassessingtheice-snowchange,thepreventionandcontrolofice-snowdamageaswellastherationaldevelopmentoficeandsnowtourismresourcesandsooninthecontextofglobalclimatechange. 41IntroductionUnderthebackgroundofclimatewarming,mostmountainglaciershavebeenintheshrinkingstate,particularlyfromtheendof1980s,whichshowsobviousresponsetoglobalwarmingandhasasignificantinfluenceontherunoff,waterresourcesuse,ecologicalenvironmentevolution,risingsealevelsandsoon(Dy-urgerov2003).AccordingtotheIPCC’sfourthassessmentreport(2007),from1960/1961to2003/2004,netmaterialflatofglobalmountainglaciersandicecaps8loss1,550×10teveryyear.In1993–2003,thesealevelrises7.7mm,asaresultofwidespreadmeltingofglaciersandicecaps.ThemonitoringresultsfromWorldGlacierMonitoringService(WGMS)indicatethatbetween1980and2005,theglobalicethicknessreducedbyanmeanofabout10.56m,andtheshrinkingtrendisaccelerating.TheglacierinChinaalsopresentssignsofacceleratingmelting.In2thepast40years,theglacierarearetreatbyameanof7%,3,790km.Theglaciersreservesareequivalentthattheannualicethicknessthin0.2m(Qinetal.2005).Therelatedstudiesshowthatunderthebackgroundofglobalclimatechange,thetrendismoreandmoreapparentsince1980s,whichisshowedbytheacceleratingreductionofglacierareaandvolume,thequitesharpmateriallossandthequick-eningwatercycleduetotheglaciersmelting(ChiewandMcMahon1994;Heetal.2003).Dyurgerov’sstudy(2003)onmaterialbalanceofabout300mountaingla-ciersallovertheworld,thealtitudeofequilibriumline,theaccumulationratioofareaandthechangeofvolumemeltin1961–1998showsthatsince1980s,theareaandvolumeofglacierissharplydecreasing.TheglacierareainAlpineshrank35%in1850–1975.By2000,thisproportionhadrisento50%,andtheshrinkingrateoftheareaisaboutfivetimesasmanyas1850–1975and117timesasmanyas1975–2000.Itisclearthattheretreatingrateissignificantlyaccelerated,whichislikelytoleadtothechangeofnaturalhazards,suchasthelandscapepatternofhistoricalperiod,theslopestability,thewatercycle,theriversedimentloadsandsoon(Mitchell2006).TheglacierareainSouth22Americahasshrankfrom2,700to2,800kmin1950–1980tolessthan2,500kmattheendof20thcentury(KatzandBrown1992).TheglacierretreatofAndeshasposedathreattothesupplyofdrinkingwater,irrigationandpowergeneration.Itisalsolikelytoformariverfloodandlakedam,thentriggermoreseriousdisasters(KatzandBrown1992).Basedontheclimatepredictionresults,theicereservesinthenorthernhemispherewillreducebyanmeanof50%by2050.Robinson(1999)demonstratesthatsince1966theannualmeansnowcoverareainthenorthernhemisphereshowsatrendofdecreaseandreducesabout10%sincethemiddleof1980s.Parkinsonetal.(1999)bythesatelliteobservationsfindthatsince1973theArcticseaiceareaalsoshowedatrendofdecline,andmayreduce2.8%since1978.During1968–2002,Antarcticseaicehasadecreasingtrend,thenorthboundofwhichretreat0.1/10atosouth.Maetal.(2004),Haeberlietal.(1998)said,accordingtothedatafromtheWorldGlacierMonitoringService(WGMS),theshrinkrateisslowbeforethe20thcentury,buttheshrinkratebegintoaccelerateafter20thcentury.Uptotheendof20thcentury,manyglacierretreat1–3km.Intherecent20years,thetropicalsnow-lineriseabout100m,whichisequivalentthattemperatureincreased0.5°C(Haeberlietal.1998).ThedataanalysisoficecloudsofNationalAeronauticsandSpaceAdministration(NASA)andICESatthinkthat 1.1BackgroundandSignificanceofTopics5thesensitivityoftheglacierchangeisunderestimatedbyscientificcommunityunderthebackgroundofthewarming.ThemeltingspeedofglacierinGreenlandandAntarcticaisfasterthanexpectation,andtherangeofthinningisexpandinggreatly,particularlyontheedgeofthesea,wheretheglacierisrapidlymelting.ThethicknessofsomeglaciersintheAntarcticfall30ft.(9.1m)everyyearsince2003,eventhedeclineratein2003–2007is50%fasterthanin1995–2003.Among111glaciersinGreenland,there81glaciersbemeltingquickly.Themeanthinningspeedofglacieris0.84m/a,theshrinkingrateofwhichexceed100m/a.ThethinningspeedofsomeglaciersintheAntarcticAmundsenbayhaveexceeded9.0m/a(IPCC2007).Sincethebeginningofthe20thcentury,theglaciersinChinagraduallytransfertotheshrinkingstate,andstepintofullretreatstage.Fromthebeginningofthe1900sto1920s–1930s,mostglacieroftheQinghai-XizangPlateauareinarela-tivelystablestate,evenforwardphase;in1940s–1960s,theglaciersareinsevererecessionperiod;during1970sto1980s,theystabilizeorappeartoasmallforward;inthelate1980s–1990s,thestrongretreatphenomenonofplateauglaciersiswidespreadgreatly,andtheretreatrateshowsatrendofincreasinginrecentyear(Puetal.2004).Since1966whentherecordsbegan,mostglacierinthemiddlesectionofHimalayanmountainhavebeeninasevereshrinkingstate(Renetal.2003).TheglaciersintheTarimRiverBasinisasawholetheshrinkingstatein1963–1999,whiletherearealsoafewoneappearingforwardphenomenon.Whenthechangesledbytheiceretreatoffset,theareaofglacierbasinandreservesreduce231,307.2kmand87.1kmrespectively,whichaccountingfor6.6and3.8%ofthe83totalin1963.Theicereductionequalto783.5×10mwaterequivalent,andit83decreasebyanmeanof21.8×10m.TheresultsofmeasuringthescopeofglacierinXizangmountainssince1915interpretthatalltheglaciersareintheshrinking2state,theareaofwhichhavereduced4719km,thereservesofwhichhavereduced36,195km,andthelengthofwhichhaveshortened1,095mwiththesealevelofendrising158m.Inthisperiod,thereductionoftheareaandreservesaccountfor4.3and4.4%ofthetotalin1915(Liuetal.2005a,b).ByanalyzingthedistributionoftheglacierofwesternNianqingtanggoulashan+MountainsinterpretedbyLandsatETM(2000),thefindsarethatthereare870glaciersinthismountain;theareaandthereserveshavereduced5.7and7%inrecent230years.Amongthem,theglacierwhoseareais1–5kmisthefastest,whichaccountfor56.7%oftotalareas.TherearealittledifferencesbetweenthesoutheastandthenorthwestofNianqingtanggoulashanMountains.Theareaofglaciersinthesoutheasternmountainsdecreases5.2%,buttheareaofglaciersinthenorthwesternmountainsdecreases6.9%.Thelengthinnorthwestslopereduces305±36m,andtheshrinkingrateis10.2±1.2m/aandtheareahasretreated2.6%(Shangguanetal.2004).ThemajorityofglacierintheYulongkashiRiverareasawholeinastablestatein1970–2001,whiletheminorityhaveasevereshrinkingtrend.Tobespecific,during1970–1989glaciersshowedatrendofexpanding,andtheareaandreservers23increaserespectively1.4kmand0.4781km,whichmayaccountfor0.12and0.19%oftheamountin1970instudyarea.However,comparedwith1970,theareaandreserversduring1989–2001reduce0.5and0.4%,respectively.Butthisregionhastheminimumglacierchangeinthearidregionofnorthwestchina 61Introduction(Shangguanetal.2008).ThemeanannualwatermaterialbalanceofWuRiverNo.143glacieris−188.6mm(about−34.6×10m),andthecumulativeamountofmaterialbalanceachieve−7,925mm,whichmeansthethicknessoficethinsmorethan8m.432Cumulativelossreach1452×10m.Theglacierareasdecrease0.22kmin1962–2000andpresentaacceleratingdecreasetrend.From1962tonow,theeasternendofWuRiverNo.1glacierhasretreated168.95m,westernendshrinks185.23m(Lietal.2003a,b,c).Thenumber,areaandreserversofglaciersinXizanganPumQuBasinhavedecreased10,9and8.4%from1970to2000(Jinetal.2004).In1969,theareainGradandois5.2%lessthanthatinpeakofLittleIceAge,and1.7%morethanthatin2000.From1969to2000,themaximumshrinkrateis41.5m/aandthemaximumforwardspeedis21.9m/a,whichmeansthattheglaciersinthisareabasicallyinastablestate;theshrinkrateisnotverysharpwiththeexistofforward(Luetal.2002).Inthe30yearsfrom1970to2000,theretreatamountofglaciersinMalanShan30–50m,andthemeanannualretreatamountis1–1.7m(Puetal.2001).TheglacierendofNaimona’nyiFengshrinksattherateofabout5m/afrom1976to2006;thebackwardspeedreach7.8m/ain2004–2006,whichperformacceleratingbacktendencyrecently(Yaoetal.2007).ThestudyofLietal.(2008)ontheglacierchangeinChinaindicatesthattheareaof18of19glaciersbasincometoappearshrink.Amongthem,theatrophyrangeof9basinslocatedinMarineglaciervalleyarebiggest.WhatistheresponsecharactersofglacierinSouthwesternChinainthecontextofclimatechange?Howdotheicelength,materialbalanceandice-snowrunoffresponsetoclimatechange?Theanswerstoabovequestionshaveasignificantmeaningtoaccessthechangesoftheregionalice-snowresourcesundertheback-groundofglobalwarmingandtheinfluencesonregionaldevelopment,andwillcontributetothereasonabledevelopmentandprotectionoficeandsnowresources.ThetotalareaofSouthwesternChinaaccountsforaquarteroftotallandarea,whichlocatedinthetransitionzonebetweenthefirstladderandthesecondladder.ThetopographyofSouthwesternChinaisvariedandcomplicatedwherehastypicalmonsoonclimateandisthemaindistributionareaofglacier.AsystemicstudyontheclimatechangeinSouth-westernChinawillcontributetoprovidingevidencefortheregionalecologicalconstruc-tion,sustainabledevelopment,andresourcedevelopment.SouthwesternChinaincludestheSichuan,Yunnan,andGuizhouProvinces,theXizangAutonomousRegionandChongqingMunicipality(directlyunderthe2centralgovernment),withanareaof2.333×106km,accountingfor24.5%ofthetotallandareaofChina(Fig.1.1).Itlocatedinthetransitionzonebetweenthefirstladderandthesecondladder,andistheoneofmostcomplicatedterrainsections,includingplateaus,mountains,hills,basinsandplains.Thetopographydeclinesfromwesttoeastandfromnorthtosouth.Therearefourgeomorphicunits:theXizangplateau,withanmeanelevationof4,500mandmanyhighermountains;theSichuanbasin,withanelevationrangeof300–700m;theHengduanMountains,consistingofaseriesofnorth–south-orientedmountainrangeswithaltitudesof4,000–5,000mandmajorrivers;andtheYunnan–Guizhouplateauwithaltitudesof1,800–1,900m(ZhaoandChen1999).SouthwesternChinaisatypicalmonsoonalclimateregion,controlledbytheSouthAsiamonsoonbutalsoinfluencedbythe 1.1BackgroundandSignificanceofTopics7Fig.1.1TheSouthwesternChinaEastAsiamonsooninsummer.ItisalsoinfluencedbytheXizanganPlateaumonsoonandthewesterlies.Therearevarioustypesofclimateinthisareamainlywithsubtropicalandtemperateclimate,soavarietyofnaturalvegetationandecologicallandscapecanbefoundhere.TheclimateofXizangPlateauisalpineplateauclimate;ThereissubtropicalandtropicalmonsoonclimateinYunnan-GuizhouPlateau,wheremanyplaceshavefourseasonsofspring;SichuanBadinhasasubtropicalmonsoonclimateandHengduanMountainshavethetemperateandsubtropicalmonsoonclimatewithsignificantverticalzonality.SouthwesternChinaisoneofthemajorglacierareaduetothetoweringterrainandthetypicalmonsoonclimate.AccordingtotheChineseGlacierInventory,therearethemostglacierofChinaintheXizangAutonomousRegion,22,468glaciers,theareaofwhichaccountfor49.02%ofthetotalglacierareainChina.Inaddition,thereare684glaciersinSichuan(1.48%oftotalareainChina)and69glaciersinYunnan(only0.15%oftotalareainChina).Itisworthmentioningthatthedistributionareaofglaciers,thenumbersandthevolumesinSouthwesternChinaallaccountforhalfoftotalamountsinChina(Shietal.2000).SouthwesternChinaisrichinthewaterresource.Itshydropowerresourcesreservesisfirstalloverthecountry,andtheminablepotentialaccountsof68%ofChina.Atthesametime,thereareenoughrainfall,theannualprecipitationofwhichistrebleasmuchasthenationalmean.Additionally,SouthwesternChinaisaregionwhereseveralminoritieslivetogetherandproducespecialcustomsand 81Introductionculture.Therefore,asystemicstudyontheclimatechangeinSouthwesternChinawillcontributetoprovidingevidencefortheregionalecologicalconstruction,sustainabledevelopment,andresourcedevelopment.Currentclimatechangeresearchesmainlyconcentratedonsomeprovinceorsomegeo-morphicunit,andmostresearchesarewantinginfurtherexplorationofinfluencingfactorsofclimatechanges.So,furtherexploringtheclimatechangeanditsinfluencingfactorswilltheshortageoftheseresearchesinthisareaandfurtherenrichtherelatedtheoryoftheresearches.During1961–2006,precipitationinwinterandspringincreased,whiletheannualprecipitationandotherseasonalrainfallreduced(TaoandHe2008).AriseintemperatureandanincreaseinprecipitationhaveproducedimportantinfluencesonriverrunoffofSouthwesternarea,eventhereismoreevidentdifferenceintheclimateandrunoffbetweenthemonsoonandnonmonsoonperiod(Youetal.2005).Wanetal.(2008,2009)analyzeatlengththespatialandtemporaldistributionoftem-peratureinLongitudinalRangeGorgeRegion(LRGR)ofYunnanandthechangeofprecipitationnLRGRofSouthwesternChina.ThestudyofFanetal.(2010)ontheclimatechangeofYunnanPlateauin1961–2004showsthattheannualmeantemperatureincreasedattherateof0.3°C/10a,andtherisingrateoftemperaturebetweeninwinterandsummerare0.33and0.26°C/10a.Theanalysisprovesthatthediurnalrangeoftemperaturesignificantlyreduced.Themagnitudeofwarmingofminimumtemperatureissignificantlygreaterthanthatofmaximumtemperatureandthemostmagnitudeofwarmingmainlyoccurinsouthandnorthwestofstudyarea.Theairtemperatureandprecipitationin1960–2008inHengduanMountainsincreaseattherateof0.15°C/10aand9.09mm/10a,respectively(Lietal.2010b).TheprecipitationoftheSichuanBasinsisrelativelystablein1958–2000,andinrecent40years,thetrendoflong-termprecipitationvariationssignificantlyreduceinthewestpartofbasin(Shaoetal.2005).Chenetal.(2008)confirmedthattheairtemperatureandprecipitationoftheSichuanBasinsshowatrendoffallingdown,andthemagnitudeoffallingintemperatureis0.029°C/10a.Thehighincidenceareaofextremehightemperatureevent(EHTE)in1961–2006inSichuan-Chongqiareaislocatedintheeastof103°E.Inthelongrun,thefrequencyofEHTEhasasharpgrowthinnorthwesternSichuanBasins;adowntrendwilloccurinthesoutheastofSichuanBasins;aslightuptrendwilloccurinthesouthwestoftheWestSichuanPlateauandsouthernmountains(Huetal.2008).In1961–2007,thetemperatureofSichuanBasinsisauptrend,andthemagnitudeofminimumtem-peratureishigherthanthatofthemeantemperatureandthemaximumoftem-perature.ThetemperatureofSichuanBasinsbegintorisefromabout1995andtheprecipitationbegintoreducefrom1990.ItisclearthatthereductionofprecipitationfromJulytoOctoberisthemainreasonofreductionofannualprecipitation(Chenetal.2010a,b,c).ThereisagreatdiscrepancybetweenthefrequencyofextremeprecipitationeventsandtheprecipitationdistributionofSichuanBasins.Inthelongterm,thefrequencyofextremeprecipitationeventsinthewestofSichuanBasinshasaslightdowntrendandauptrendintheeastpartofChongqing,thelineartrendofothersareaisquiteobviousexpectthem(Huetal.2009). 1.1BackgroundandSignificanceofTopics9Tangetal.(2009)preliminarilyanalysisandresearchthechangetrendoftotalcloudcoverintheXizanganareas.TheresultsindicatethattotalcloudcoverwassignificantlyreducedoverthemostofXizanganregions,amongwhichthelossofthewesternNaquzhongismaximum,upto2.32%/10a.Thereisapositivecor-relationwithtotalcloudcover,precipitationandrelativehumidity(RH);whilethereisanegativecorrelationwithtotalcloudcover,sunshinehours,meantemperatureandthediurnaltemperaturerange.HurstindexdemonstratethatthetotalcloudcoverdecreaseoverthemostofXizanganregions,andthistrendwillnotchangeinashortperiod.Theannualmeantemperatureriseattherateof0.26°C/10a,whichissharplyhigherthanrisingrateofChinaandworld.Andthediurnaltemperaturerangesharplydecreaseexpectsummer(Du2001).In1971–2000,thechangeofannualprecipitationpresentsapositivetrend.Theinclinationrateofprecipitationis1.44–66.6mm/10a.AnnualchangesofthenumberofprecipitationdayshaveanegativetrendinNgariPrefectureandNyingchiPrefecture,whereasitisapositivetrendinthemidwestofNagquprefectureandthenorthofChamdoPrefecture(DuandMa2004).During1971–2005,themaximumpotentialevapotranspirationinXizangPlateaureduce,whichis−24.0mm/10a.Theseasonaltrendalsopresentreduce,especiallywinter.However,surfacemoistureindexsharplyincrease,whichis0.04/10a.Particularlyinrecent25years,theuptrendisgreatlyenlarging.Soafterstudy,aconclusioncanbegiventhattheincreaseofprecipitationandrelativehumidityandthedecreaseofthediurnaltemperaturerangeisthemainreasonofmakinghumidindexincrease(Duetal.2009).Wangetal.(2010)pointsoutthatthedistributionofthresholdvalueoftheprecipitationandextremerainfallinYunnan-GuizhouPlateauhasagreatdifferenceduringfloodseasonin1961–2007.Thethresholdvaluehaslittlerelationshipwithamountofprecipitationduringfloodseason,buthasanegativerelationshipwithaltitude.ofstations.Thechangtrendinrainfallisnotobvious,buttherainydaysreducesharply.In1961–2006,84.2%ofstationsappearedatrendofreducedvisibility.Themaximumamountofreductionis−11km/10aandtheminimumis−1km/10a.Thereducingmeaninclinationrateofclimatewas0.96km/10ain1961–1979and1.6km/10ain1980–2006.Themeanvisibilityofplateaureduceto27kmfromabout34kmin1960s.Itisprovedthatthereasonofthedecreaseofvisibilityandtheincreaseofextinctionhaveacloserelationshipwiththepollutantsconcentrationdischargebyhuman(Zhengetal.2010a,b).Thesunshinedaysof85%ofstationsreducein1961–2005inYunnan-GuizhouPlateau.Thereductionrangeisbetween12.2and173.7h/10a.Itisshowedthattheincreaseofplateautroposphericaerosolsandthepollutantconcentrationisthemainreasonofthedecreaseofsunshinedays(Zhengetal.2010a,b;Yanetal.2004,2005).Maetal.(2006)confirmedthataseriesofchangesappearedafter1940sinQinghai-XizangPleteau,WesternSichuanPlateauandYunnan-GuizhouPlateau,forexample,temperaturerise,precipitationandhumidityincrease.WhilethetemperatureinthesouthwestandnortheastofSichuanBasinhasanobviousdowntrend,whichindicatethattheclimatechangeofSouthwesternChinaisoutofsyncwiththeglobalwarming.StudieshaveshownthattheprecipitationresourceoftheplateauareainSouthwesternChinaexcludingXizangPlateauincreaseinrecent 101Introduction40years,whereas,thatoftheEasternChinadecrease,expectChongqing(Liuetal.2007).Someresearchesindicatethattheminimumtemperatureingeneralwasheatingup,andinJanuarytheminimumtemperaturewarmfasterthaninJuly.ThewarmperiodhappenedinWinterofthe1980sratherthaninsummerofthe1950s(Banetal.2006).AccordingtoannualprecipitationdataofSouthwesternChinain1951–1999,thesummerprecipitationpresentaninterannualcycleof3–4yearsandaninterdecadalcycleof10–16years,andthesummerrainfallandthedistributionofdroughtandfloodhaveagoodcorrelationwithSouthAsiaHigh(SAH)(Duetal.2002).Theresearchesshowthatthecloudcoverchangeof85stationsinSouth-westernChina(excludingXizangprovince)hasaobviousseasonalcharacteristic:thedistributionoftotalcloudcoverandlowcloudcoverappearsonadiminishingscalefromeasttothewestinspring,autumnandwinter,whichisoppositetothatinsummer.Theannualmeantotalcloudcoverandsummertotalcloudcoverareyearlytodecreaseoverthemostofregions,andwintertotalcloudcoverdecreaseinthenorthofWesternSichuanPlateauandsouthandeastofYunnanprovince.ThelowcloudcoverchangeisstableinmostareasbutdecreaseinSichuanBasin.ThereisasignificantnegativecorrelativitywithtemperaturefieldandtotalcloudcoverinSouthwesternChina,butthereisnotanobviouscorrelativitywithtemperaturefieldandlowcloudcover(Zhengetal.2010a,b).Inaddition,somestudieshaveprovedthatthemainreasonofthedroughteventisthereductionofwatervapourtransportresultedfromtheatmosphericcirculationanomalies(WangandLi2010;Zhengetal.2010a,b).Inconclusion,currentclimatechangeresearchesmainlyconcen-tratedonsomeprovinceorsomegeomorphicunit,andmostresearchesarewantinginfurtherexplorationofinfluencingfactorsofclimatechanges.1.2AdvancesinClimateChangeResearch1.2.1TheFactofClimateChangeThemaindirectionofclimatechangeresearchisalwaysreconstructingcanonicalsequenceofclimatechangeinalongtimescale.In17thand18thcenturies,withthemeteorologicalobservationinstrumentsinventedonebyone,themeteorologicalobservationisfundamentallytransferredfromqualitativedescriptiontoquantitativemeasurement,whichmarkedthebeginningofthemodernmeteorology.China’smeteorologicalobservationstationshavehadonehundredyearsofhistory,whichwillcontributetoprovideauthenticobservationdataforclimatechangeinnearlyonecentury(Wu2005).Basedonthemeteorologicalobservationdata,alargenumberofscholarshavecarriedouttheresearchonsequenceofclimatechangeinalongtimescale.In1960s,Mitchell(2006)constructedareliablemeantemperatureseries.After1980s,someresearchersconstructedalotofmeantemperatureseriesbysortingandinterpolatingtemperaturedatafromdifferentplaces.ThetemperatureseriesconstructedbyJones(1988,1994),JonesandMoberg(2003)andVinnikovetal.(1990),asthemosticoniconeamongthem,wasrevisesandaddedmorethan 1.2AdvancesinClimateChangeResearch11oncetoimprovethelandandseasurfacetemperaturedataandfinallywasusedbyIPCC.ThetemperaturevariationsequencesofcenturyinChinawasconstructedbyWangetal.(1990,1994,1998),WangandYe(1995),Shietal.(2004),TangandRen(2005).Thescaleoftheprecipitationintimeandspaceisverysmall.Thereneedalotofobservationstationstoestimatethemeanglobalprecipitation,butinfact,precipitationobservationsdataismuchlessthantemperatureobservationdataanditismoredifficulttoestablishglobalmeanprecipitationsequence.Bradleyetal.(1987)setupmeanlandprecipitationsequenceoftheNorthernHemisphereduring1850–1980bytherainfallobservationrecordsofnear1,500stationsintheNorthernHemisphere.OnthebasisofBradley’sstudy,Diazetal.(1989)analyzedtheprecipitationintheSouthernHemisphere,andemergedthemtoanalyzetheglobalmeanprecipitationindexin1890–1986.Hulme(1995)sortedglobalpre-cipitationobservationsdataintothegridmeanprecipitationandcalculatedtheglobalmeanlandprecipitationin1900–1988.Inrecentyears,Chinesescholarshaveconductedacomprehensiveandsystematicresearchontheglobalprecipita-tionvariationbyusingthelatestandthemostcompletegloballandprecipitationdata(Shietal.2004;YangandShi2003;Liuetal.2006a,b).Chenetal.(2004)alsohaveanalyzedChineselongprecipitationsequencechange.Theimportantdirectionofclimatechangeresearchisalwaysthesystemicunderstandingofclimatechangetrendinthelongtimescale.JonesandMoberg(2003)foundthattheglobaltemperaturevariationdidnotfluctuatein1881–2003.ThetemperaturevariationsofSouthandNorthHemisphereareveryclosetoglobaltemperaturevariation,butthevariedrangeoftheNorthHemisphereisbiggerthanglobaloneandthevariedrangeoftheSouthHemisphereissmallest.Hulmeindicatesthatglobalmeanprecipitationhasaslightuptrendin1900–1988,approximatelyadd1.6%.Precipitationismuchlessexceptin1950s–1960sand1970s–1980s.Shietal.(2004)showedthattheglobalprecipitationvariationincreasesinwinter,besides,thereisnotobviouschangeinotherseasons.TangandRen(2005)pointedoutthattheannualmeantemperatureincreased0.79°Cin1905–2001.Thetemperatureremarkablerisein1930s–1940sandthemidof1980s,butthetemperatureisquitelowinotherperiods.ComparedwiththeglobalmeanandthemeanofNorthHemisphere,thewarmingintheearlyandmidpartof20thcenturyismoresignificantandthelowtemperatureisalsoobvious.Intherecenthundredsofyears,warmingmainlyoccurredinwinterandspring.Overthepastyears,somescholarsbegantostudytheclimatechangeforpast50yearsinmostareasofChinaandconfirmedthesignificantrisingtrendoftemperature(Liuetal.2007;Banetal.2006;DongandWu2008;Yuetal.2003;Wangetal.2008;Caietal.2003).Chenetal.(2004)showedthatthepluvialageoftheareasineastof100°Eare1920,1930–1940,1950,1973,theearlyof1980and1990.Amongthem,theprecipitationin1920sand1950sismost.Fortheareasineastof100°E,theprecipitationinChinabegantodeclineafter1950s.Inaddition,thereisalargenumberofresearchesofregionalprecipitationvariation(Tangetal.2005;Caietal.2008;ZhangandFeng2010),whichrevealthetemporalandspatialvariationcharacteristicsoftheregionalprecipitationinChina. 121IntroductionInrecentyears,theattributionofclimatewarminghasgraduallybecomethehotspotanddifficultyofclimatechangeresearch.TheconclusionofIPCC’sfirstassessmentreportin1990wasthattheclimatechangeinrecentyearisresultedfromnaturalfluctuationsorhumanactivityorthecommonactionofbothtogether.In1996,theIPCC’ssecondassessmentreportpointedoutthatalthoughitislimitedtodisplaytheinfluenceofhumanactivityonglobalclimateandthereissomeuncertaintyinthemainfactor,moreandmorefactshowthattheinfluenceofhumanactivitiesontheclimatehasbeendetected.In2001,bylatestandauthoritativeexampletheIPCC’sthirdassessmentreportindicatedthatthe66%ofglobalwarminginthepast50yearsmaybecausedbyhumanactivities.In2007,accordingtotheIPCC’sfourthassessmentreport,theconclusionwasgavethatthemainreasonofglobalwarmingisprobablythehumanactivities,andtheprobabilityismorethan90%.Itisalsocontroversialwhethertheglobalclimateisresultedfromthehumanactivityornaturalprocess,whichalsoisafocusissueoftheglobalclimatechangeresearchfornowandforquitealongtimetocome.Daietal.(2010)think,aftersummarizingsomestudiespublishedbyNaturein2009,thatmoreresearchesontheclimatechangeexistinthecarboncycle,cryosphere,marineandpalaeoclimatereconstructionarea.Therealsoaresomeexistinginthemechanismresearchofclimatechangeandaerosol.It’sworthnotingthattheresearchachievementsinthegreenhousegasesreducewhiletheresearchesoncarbonturningwhitehot.Amongtheachievements,thestudyonclimatechangesismost,whilethestudiesontheimpactandpolicyresponsesarequitefewaswellasthestudyonestimatesofclimatechange.Itreflectstheresearchstatusquoofglobalclimatechangethatthemechanismstudyofclimatechangeurgentlyneedtostrengthen.Comparingseasonalchangeofglobalsurfacetemperaturebetween1954–2007and1990–1954,itisfoundthatthephaseofannualcycleoflandsurfacetemperatureinthetropicsbringsforward1.7dduring1954–2007.Thisisobviouslyinconsistentwithearlychangerate.Theresearchworkersholdtheideathattheearlychangerateisdominatedbythenaturalchange,butthechangesofrecent54yearsmaybecausedbyhumanactivities.Theyalsocombinethesatellitedataandthetemperaturedatainlongtimescaleof42weatherstationsattheSouthPole,andreconstructthesurfacetemperaturesequenceattheSouthPole.Thenaconclusioncouldbemadethatoverthepast50years,thewarmingrateofwesternSouthpolehasexceeded0.1°C/10a.Particularlyinwinterandspring,therateissharplyremarkable.Themodelingresultofglobalcirculationpatternsindicatesthatthespatialdistributionandthelong-termchangetrendsofantarctictemperaturevariationarenotdirectlyrelatedtotheenhancementoftheantarcticwesterlies.Inrecentyears,theextremetemperatureandrainfalleventshavebeenmoresensitivethantheresponseofmeansequencetoclimatechangeandhavereceivedthewidespreadattention(Kunkeletal.1999;Easterlingetal.2000).Theresearchesofextremeweatherhavebeencarriedoutinsomeplaceallovertheworld,forexample,theAsia-PacificRegion,CentralandSouthAsia,SouthAmericaandsoon.Thesestudiessuggestthattheextremetemperatureindexsharplywarm,eventhemagnitudeofwarmthindexismorethanthatofcoldnessindexandnightindexismorethandayindex.Thechangetrendofextremeprecipitationindexisvery 1.2AdvancesinClimateChangeResearch13stablebecauseofregionaldifferences,soitisdifficulttojudgethegeneraltrendchange.Thestudieshavealsoshownthattheindexrelevantwithtemperaturepresentsobviouschangesinthepast50years,whiletheindexrelevantwiththeprecipitationpresentsregionaldifferences.Theanalysisofglobalclimateextremechangeshowsthattheextremetemperatureindexrisesignificantlyinthe20thcentury,especiallycoldnessindex.Thistrendwillbecomemoreobviousinfuture20years,whiletheprecipitationindexwillshowawettingtrend(Frichetal.2002;Alexanderetal.2006).TheresearchesofclimateextremechangeinChinashowthattheextremetemperatureindexalsopresentasignificantwarmingtrend,particularlythecoldnessindex.Intermsofseasons,thechangeinwinteristhemostsignificant;intermsoftheregionaldifference,themagnitudeofwarminginNorthernChinaarebiggest.ThechangesofregionalextremeprecipitationinChinahascertainregionalfea-tures.Forexample,theextremeprecipitationintheYangtzeriverbasinmainlyoccurinsoutheastandsouthwestpart.sincethemidof1980s,thecrestvalueofextremeprecipitationeventsintheupstreamoftheYangtzeriverbroughtforwardtoJune,nearlysynchronizingwiththatinthemiddleandlowerreachesoftheYangtzeriver,whichwillinevitablyincreasetheriskoffloods.Since1990s,thefrequentoccurrenceoffloodiscloselyrelatedtothechangesoftimeandspacedistributionofextremeprecipitationintheYangtzeriverbasin.However,inthepast20–30years,theextremeprecipitationinWesternChinaincreasedmoreobviously.Inrecent40–50years,theclimateofXinjianghasbeenwarmingandtheprecipitationhasbeenincreasing,particularlysince1987.Accordingly,therunoffrisesharply.Itisfoundthattheprecipitationincreasingismainlybecausetherainfallintensityincrease(Lietal.2011a,b;Zhaietal.1999,2003;2005).Intermsofthenationalmeanprecipitation,thetrendofprecipitationchangeisnotobviousinthepast50years,butitsspatialdistributionisveryuneven.ThearidificationisveryseriousinNorthChinainthepast50years.Thechangetrendofstrongprecipitationandregionaldistributionofprecipitationisveryconsistent,displayedbythereduceddaysoftheheavyrain.Therefore,thechangetrendofextremeprecipitationreflectedbytheregionalhistoricalclimaterecordsinChinaatleastisinlinewithglobaltrend,themaincharacteristicofwhichisstillregional(Zhaietal.2005).Tosumup,overthepastdecades,China’swidespreadprecipitationtrendismainlyinthewesternregion,especiallyinthenorthwestregion.Andtherearethebigregionaldifferencesoftheprecipitationvariationtrendintheeasternmonsoonregion.TherecentstudyfurthersupportthatmoreextremeprecipitationeventswillhappeninChinaandthemeanintensityandmagnitudehasdifferentdegreesofincrease,especiallyinthe1990s(Jiangetal.2007).Qinghai-XizangPlateauisalwaysthekeyareaofclimateextremeresearchinChina.Liuetal.(2006)thinkthatdailymaximumandminimumtemperatureandthelengthofgrowingseasoninthecentralandeastofQinghai-XizangPlateauallsignificantlywarmin1961–2003.Themostremarkablewarmingoccurinwinterandsummer.Inaddition,thischangepresentabiggermagnitudeofwarmingathighaltitudesthaninlowaltitudes(Liuetal.2009).ThestudyofYouetal.(2008)alsoprovethattheextremetemperature 141Introductionindexrosesignificantlyin1961–2005inthecentralandeastofQinghai-XizangPlateau,butthechangetrendofextremeprecipitationisnotsignificant.Theradiationorsunshinedurationisoneoftheimportantdrivingforcethatimpactonclimatechange,theplanetecosystemandhumanactivities.Forexample,itcandirectlyorindirectlyaffectthesoilmoisturethroughphotosynthesisandwaterevaporation,andwillbepaidmoreattentionintheclimatechangeresearch.Moststudieshavefoundthattheglobalsolarradiationreduceonebyoneyearinrecentyears,andthisphenomenoniscalled“globaldimming”(StanhillandCohen2001;Liepert2002;Alpertetal.2005;Wildetal.2005).Inaddition,thisresultalsocanbeprovedbymoststudiesontheradiationorsunshinedurationofareasallovertheworld,suchasAmerica,WesternEuropeandthemostregionsofCentralEuropeandIndia(Liepert2002;Power2003;NorrisandWild2007;Sanchez-Lorenzoetal.2007;Kumarietal.2007).Thesestudiesmake“globaldimming”becomeahotspotinthefieldofglobalchangeresearch.Asitisthecaseinmostareasoftheworld,ithasalsobeenwidelyreportedthattheradiationorsunshinedurationofmostareasinChinaisyearlytoreduce,suchasNorthwesternChina,Qinghai-XizangPlateau,NorthernChina,EasternChina,andsoon(Chenetal.2010a,b,c;Yangetal.2004;Zhangetal.2004;Yangetal.2008a,b;XuandZhao2005).Moreover,alargenumberofstudiesonthechangeofthesunshinedurationatthenationallevelalsoconfirmthatthereductionofthesunshinedurationiscommoninChina(KaiserandQian2002;Renetal.2005a,b;LiangandXia2005;Cheetal.2005).Generallyspeaking,themainfactorsimpactingonthechangeofsolarradiationandsunshinehoursareastronomy,geography,geometry(surfaceazimuth,digangle,solarazimuthandsolaraltitude,etc.)physics(water-vaporabsorption,scatteringofairmolecules,dustandscatteringofatmosphericcomponentssuchasO2,N2,CO2,O3)andmeteorology(reflectionofcloudsandenvironmentalele-mentsetc.)etc(ErtekinandYaldiz1999).Inaddition,alargenumberofstudiesonthereductionofthesunshinedurationatgloballevelpointedoutthatthereasonsofglobaldimmingarealsoincludetheincreaseofatmosphericaerosolandotherairpollutantscausedbythehumanactivities,theeffectoftheatmosphere,thecloud’sopticspropertyandtheaerosolandtheincreaseofcloudcover(NazarenkoandMenon2005;CutforthandJudiesch2007).GrimenesandThue-Hansen(2006)thoughtthat“globaldimming”maybecausedbythebackdonationofglobalwarming.Pinkeretal.(2005)attributedthe“globaldimming”tothechangeofcloudcover,theincreaseofhumanactivities,theaerosolsandthelowatmospherictransparencyalongwiththevolcaniceruptions.Qianetal.thoughtthefogorhazeresultedfromthedischargesofalargenumberofairpollutantsreflectorabsorbtheradiationfromthesuntoreducethesolarradiationtolandsurface,althoughsunnydaysareontherise.Furthermore,manysubsequentresearchesalsoconsiderthattheincreaseofatmosphericaerosolisthemaindrivingforceresultinginthedecreaseofsolarradiationandsunshineduration(Renetal.2005a,b;Chenetal.2006;GuoandRen2006;Shietal.2007;Qianetal.2007).Pinkeretal.(2005)alsofoundthatthemagnitudeofglobaldimminghasbeenreducingsince1990sandtheyattributeittotheloweringofpollutionlevels.Wildetal.(2005)furtherfoundthattheloweringconcentrationofatmosphericaerosolinthemostregionsofthe 1.2AdvancesinClimateChangeResearch15worldcanbeattributedtodrasticandeffectivemeasuresinrecentyears.Alpertetal.alsobelievethattheimpactofhumanactivitiesonclimatechangeisattheregionallevelratherthanatthegloballevel.Inotherwords,thephenomenonofthereductionofsunshinehoursshouldbeconsideredasregionaldimmingratherthanglobaldimming.Thechangeofwindspeedisanimportantsymbolofchangesoftheatmosphericcirculationsystem.Thechangeofgroundwindhasreceivedmoreattentionfromthepublicandacademicfieldbecausetheloweringwindspeedinmostpartsoftheworldinrecentyearshasposedagreatchallengetothedevelopmentandutilizationofwindenergyresources(Pryoretal.2005).Theremanystudiesfoundthewindspeedisalsoanimportantreasonoflessevaporationofpan(Rodericketal.2007,2008;Rayner2007).Robertetal.(2010)carriedonaresearchintothewindchangeatmid-northernlatitudesfor1979–2008bythedataof882surfaceobservationstations,andmadeitclearthatthewindspeedinmostpartsofstudyareareduce5–15%.PirazzoliandTomasin(2003)fromtheobservationdataof17stationsinthecoastalareaofItalian,foundthatwindspeeddecreasedsignificantlyinthemidof1950–1970,butitdecreasedslightlyevenappeartoincreasefrom1980.Brazdiletal.(2008)alsoreportedthewindspeedinmostregionsoftheCzechrepublicreduced.Fromthelate1940stothemidof1990s,boththeannualmeanwindspeedandthemeanwindspeedinwinterinthewestcoastofCanadadecreased(Tuller2004).Andfrom1973to2005,thewindchangeintheUnitedStatesischarac-terizedbydowntrend(PryorandLedolter2010).ThewindspeedinAustraliasignificantlyreducedbyrateof−0.009m/s/aover1975–2006,andabout88%oftheallweatherstationsshowedthewindspeedreduced(McVicaretal.2008).In1962–2002,themediumwindsevents(mean10timesinayear)andstrongwindsevents(mean2timesinayear)inNewZealandalsoshowedadecreasetrend.(Smitsetal.2005)ThewindspeedfromthemajorityofsevenweatherstationsinMinnesotaintheUnitedStatesshowedadowntrendinrecent22–35yearsexpectonewhichappearedslightrise(Klink2002).However,intheBalticregion,theannualmeanwindspeedincreasedfrom1953to1999andthewindspeedofmorethan75%oftheareaincreasedsignificantly(PryorandBarthelmie2003).WangandLi(2004)madeastudyonthewindspeedin1951–2000inChinaandindicatedthatthereducingtrendiscommon,andthebiggestreductionoccurredinthenorthwesternregionandinwinter(Xuetal.2006a,b).conductedafurtherstudyonthewindspeedchangein1969–2000inChina,andfoundthattheannualmeanwindspeeddecreasedabout28%,themeanminimumratewas−0.021m/s/aandthelargestreductionmainlyoccurredinwinterandsummer.Onthebasisofthelatestobservationdatafrom652weatherstations,Gaoetal.(2010)foundthattheannualandseasonalwindspeedofmoststationsinChinashowedasignificantdecreasein1969–2005,butthereisaslightincreaseafter1991.Intheupper,middleandlowerofthetroposphere,theannualmeanwindspeeddecreasedatthe−1rateof−0.10–0.17ms/10a.Thefurtheranalysisconfirmedthattheloweringsurfacewindspeedisnotonlycausedbytheatmosphericcirculationchange,butalsotheenvironmentchangearoundweatherobservationstationsresultedfromtheurbanization.Theacceleratingurbanconstructionandtallbuildingshascausedan 161Introductionobviousblocktowindspeedobservationofstationsinurbanareas(Lietal.2010a,b).From1961to2004,thewindspeedofHeilongjiangprovinceappeareddowntrendduetothesignificanttemperatureriseandmassivechangesinthelandusecausedbytheurbanization(Zouetal.2010).In1961–2007,thewindspeedchangeofChongqingwasinareducingsituationandthemagnitudeofloweringhadbecomemoreandmoreobvioussince1974(Lietal.2010a,b).TheannualmeanwindspeedinmoststationsofNorthernChinareducedattherateof−0.2to−0.5m/s/10ain1957–2006(RongandLang2008).Throughtheanalysisoftheobservationdataof104stations,thewindspeeddecreasedsignificantlyat1951–2006intheNorthChinaPlaneandthemagnitudeis−0.16m/s/10a(Yangetal.2008a,b).InJiangsuprovince,theannualmeanmaximumwindspeedfluctuatedin1975–2008anditsgeneraltrendistoreduce(Chenetal.2010a,b,c).AlargenumberofstudieshavealsoshownthatthereductionofwindspeedisnotonlythemainreasonofsurfaceevaporationdropintheQinghai-Xizangplateauandalloverthecountry,butalsothekeyreasonofcausingsandstormreduce(Qianetal.2002;Wangetal.2004;Huangetal.2006).Therearesomereasonscausingthereductionofsurfacewindspeed,whichdisplayedbyasfollows:(1)thechangeofcirculationsystematlargescaleorthemicroscaleweakeningofsynopticsysteminthecontextofclimatechange(Luetal.2007;Seideletal.2008)(2)theincreasingsurfaceroughnessofweatherobser-vationstationsorthestructuralchangeofboundarylayer(Lynchetal.2004)(3)theinstrumenterrorortheobservationerror(DeGaetano1998;McKeeetal.2000).Robertetal.(2010)foundthattheotherreasonofwindspeedreducing10–50%intheNorthernHemisphereisthechangeofsurfaceroughness,especiallythelandcoverchangeinEurasiancontinents,basedonthereanalysisdata.InChina,thewinterwarminginthenorthernregionsislikelytobethemainreasonofthereductionofwintermonsoon.While,thetemperaturedecreaseinsummeroccurredinthecentralpartsofSouthernChinaandthesignificantrisingtemperatureoccurredinSouthChinaSeaandthenorthwesternPacificmaybeassociatedwiththeweakeningofthesummermonsoon(Xuetal.2006a,b).Gaoetal.(2010)furtheranalyzedandconfirmedthatreductionofthepressuregradientforceinthelowerofthetroposphereistheotherkeyreason,andpointedoutthatthewindspeedchangeiscausedbyclimatechange.Thechangeofsurfacewindspeedhasimportantenvironmentalandsocialeconomicmeanings.Zhouetal.(2006)hadconfirmedthattheloweringwindspeedhascausedthereductionofwindpowerinthePearlRiverDeltaregion.Liuetal.(2005a,b)heldanideathatthereducingwindspeedandthechangingwinddirectionhadbroughtgreatchallengeforthedevelopmentofregionalwindenergyresourcesinthebroadaridzonecenteredbytheErdosPlateauinInnerMongolia.Sothestudyonthechangeofwindspeedishelpfultohaveacomprehensiveunderstandingofclimatechangeanditsinfluencetoenvironment,ecologicalsystemandsocialeconomy. 1.2AdvancesinClimateChangeResearch171.2.2TheMechanismofClimateChangeHayetal.(2002)thoughtthefactorsofaffectingclimatechangecanboildownelevenones.Combiningtheirswithothersresults,Zhangetal.(2005a,b)reducedthesefactorsinto16ones,whicharethesolarradiation,thecosmicdustconcen-tration,theearth’sorbit,thecontinentaldrift,theinfluenceofmountainuplifttoatmosphericcirculationandenvironment,theoceancurrents,theseaice,thedis-chargeofgreenhousegases,theatmosphericaerosolconcentration,thepolarstratosphericcloudcover,thepolarvegetation,the“ironhypothesis”associatedwithdustaerosol,thetransformationfromC3toC4ofplants,thecelestialbodycollision,thevolcaniceruptionsandthecirculationincore.Forthereasonsofglobalwarminginthe20thcentury,itisgenerallybelievedthattheyarerelatedtotheincreaseofconcentrationsofgreenhousegases(IPCC2007),althoughthisideaisstillcontroversial.Renetal.(2005a)gavethekeyfactorsthatmayimpactonthechangeofthesurfacetemperatureinnearly50or100yearsinChina,includingnaturalfactorsandhumanfactors.Thenaturalfactorsmainlyconsistofthenaturaleventsdominatedbysolaractivityandvolcanicactivityandthechangesdominatedbythechangesofvegetation,iceandsnowandatmosphericcirculation.Thehumanfactorscontainthechangesofgreenhousegas,landcoverandatmosphericaerosols.Theresultsofthestudiesaregenerallybelievedthatthevegetationcoveragechangeeventuallyleadtothechangesofregionalprecipitation,circulationsituation,atmospherictemperatureandhumiditybychangingthesurfacealbedo,roughnessandsoilmoistureandimpactingonradiationbalanceandwaterbalance.LiandDing(2004)summarizedthedomesticandforeignrelatedresearchesinrecent10years,especiallytheinfluenceofvegetationchangesonChineseregionalclimate,andfoundthatthemoststudiesthoughtawiderangeofvegetationdegradationcouldresultinsurfacetemperaturerise,weaknessofEastAsiansummermonsoon,decreaseofprecipitationandworseningdrought.Therewassomecontroversytotheeffectsofurbanizationtowarming.Someresearchessuggestthattheinfluenceofthechangesoftheurbanizationandlandusetothetemperaturerecordafter1950canbeignoredinhemisphericandcontinentalscale.ThestudyofJonesetal.(1990)haveshownthatthemagnitudeoftheinfluenceofurbanizationinhemisphericorglobalscaleissignificantlysmallerthanthatininterdecadalorlongertimescale.Recently,Parkerfoundthatthewarmingtrendofminimumnighttemperatureintheconditionsofcalmdoesnotstrengthenbyusingrecordsoftheglobalobservatory,whileitismostlikelytobeaffectedbytheurbanheatislandduringthisperiod.Therefore,thelong-termwarmingtrenduponalllandglobalwideisunlikelytobeinfluencedbytheenhancedurbanization.IntheUnitedStates,itisalmostimpossibletoseparatethechangetrendofthetemperatureinthecountrysidefromthatinthecity(PetersonandOwen2005).Buttherearealsosomeresearchespointoutthattheclimateinthecityisgeneralwarmerthanthatinthesuburbsandtheurbanheatislandhasasignificanteffectonthetemperaturerise.Forexample,in1973–1996theurbanheatislandmadethetemperatureofSeoulinSouthKorearise0.56°C(KimandBaik2002).Otherresearchesalsoconfirmedthattheurbanheatislandmadetemperature 181IntroductionofSouthKoreain1968–1999increase0.40°C(Choietal.2003).SomestudiesalsohaveshownthattheurbanheatislandhassignificantcontributionstotemperatureriseofSoutheasternChina(Zhouetal.2004).Atpresent,itiscommonthattheglobalwarmingisconsideredastheworseninggreenhouseeffectcausedbytheincreaseofgreenhousegas.Actually,thiscon-clusionhascertainbasistosomeextent.However,intermsofthescientifictheory,theimpactofincreasinggreenhousegasescausedbyhumanactivitiesisnottheonlyreason(Lietal.2003a,b,c).Basedonsomeexistingresearches,thesolaractivitymayalsobeanotherimportantcauseofglobalwarminginthe20thcentury.Theinfluencesofsolaractivitiesmainlyincludesthedirectinfluenceofsolarradiationandtheindirectinfluenceoftriggeringgeomagneticfieldchanges.Thechangesofearthmagneticfieldcanimpactontheatmosphericcirculationandclimatechangethroughthedynamicprocessandthermalprocess(Lietal.2003a,b,c).Zhouetal.(2007)summarizedalargenumberofstudiesandmadeaconclusionthattheweatherandtheclimateareremarkablyaffectedbysolaractivityinanyscale.Inrecentyears,therelationshipsbetweenclimaticelements,suchasglobalcloudcover,thewintercycloneoftheNorthAtlanticandsoon,andthespaceweatherevents,suchasthechangeofcosmic-rayflux,SolarEnergeticParticleandsoon,arediscoveredonebyone.Onthisbasis,Zhouetal.(2007)proposedthemechanismthatthesolaractivitiesdrivesclimatechange.Itsbasicideasarethespaceweathereventsaffectweatherandclimatebychangingthephysicalcharac-teristicsofcloud.Thecoreistherelationshipbetweenthesolaractivitiescausedbyspaceweathereventsandthemicrophysicalprocessofcloud.Atpresent,thetheoryofspaceweathercanbedividedintoion-inducednucleationmechanismandTinsleymechanism.Zhongetal.(2004)foundthattheprofilesinthesouthedgeofTarimBasinrecordedtheclimatechangesincenearly4ka,especiallythemeanparticlesizeofsediments.Thefluctuationsindecadeandhundredscalearecon-sistentwithGreenlandGISP2temperatureindicatorsofoxygenisotopeincores14fromiceandtheatmosphericCcurve.Andthemostofcyclessummarizedbyanalyzingtherednoisespectralhaveconsistencywiththecycleofthesolarradi-ationchanges,suchas196,121,97,121,45and33–30years.Combinedwithawiderangeofregionalcorrelation,itisfurtherprovedthatthesunradiationmaybeanimportantdriverforceofregionalandglobalclimatechangesintentohundredscale.WhatthemostimportantisthatthesurfacetemperaturevariationsintheNorthernHemispherehavearemarkableconsistencyandthepositivecorrelationwiththesunspotcyclessince1940.Thisseemedtoconfirmtheimportantroleofthesolaractivitytotheevolutionoftheearth’sclimatesystem.Theinterannualvariabilityoflarge-scaleatmosphericcirculationisoneofthemaindriversofclimatechange.Huang(2010)thoughtthevariationofEastAsiamonsoonclimatesystemsisnotonlyrelatedtothevariationofocean,landsurfaceprocessandsnowandice,butalsothedynamicprocessofthissystem.Toalargeextent,theinterdecadalchangeofEastAsiamonsoonunderthisrelationshipisassociatedwithmajordroughtandflooddisasterinChina.ThestudyshowsthatEastAsiamonsoonsystemhasaobvioustemporalandspatialvariation.Among,thesummermonsoonsystemhasaquasitwo-yearlyoscillationininterdecadalscale, 1.2AdvancesinClimateChangeResearch19andappearsamarkeddecresaseininterannualchangefromthelateof1970stonow.ThischangeisparticularlysignificantinNorthChina.WhileEastAsianwintermonsoonhasaquasifour-yearlyoscillationininterdecadalscaleandalsoappearsamarkeddecreasesininterannualchangesincethelateof1980s,whichcausethecontinuouswarmwinterinChina(Huangetal.2008).Byanalyzingtheevolutionofinterfacebetweeneastwindandwestwind,itisconfirmedthattheshiftfromeastwindinwintertosouthwestwindinsummerhappenedintheloweroftroposphereoftheAsianmonsoonregionfirstoccurredintheeasternbayofBengalduetothespringwarmingoftheXizanganplateau,alongwiththeintenseconvectivepre-cipitation.Therefore,theeasternbayofBengalandthewesternindochinaarethefirstregionwheretheAsianmonsoonoccurs.Atthesametime,itisalsopointedoutthatthecirculationarousedbythesummerwarmingoftheIranianPlateauandtheQinghai-XizangplateauisnestedinthethermalcirculationofEurasia,whichstrengthenthesummermonsoonoftheEastAsianandaggravatedthedroughtinCentralAsiaandWestAsia.Moreover,thefluctuationsarousedbythesummerwarmingoftheIranianPlateauandtheQinghai-XizangplateauexercisesagreatinfluenceonclimatepatternofEastAsianinsummer(Wuetal.2004).Therela-tionshipoftheprocessesofterrestrialcarboncycleandgreenhousegaseshasbecomeaconcernofclimatechanges.WhichroletheChina’sterrestrialecosystemsplaysinglobalcarboncycleisamajorenvironmentalissuescommonlyconcernedbythedomesticandinternationalscientists.Piaoetal.(2009)comprehensivelystudytheterrestrialcarboninChina,andtheresultsshowedthatthemeangrowthperyearofcarboninChina’sterrestrialecosystemis0.19–0.26PgCfrom1980sto1990s.ThecarbonsequestrationofChina’sterrestrialecosystemisequivalentto28–37%ofCO2dischargesinChina,whichismuchmorethanthatofEurope(7–12%),closetotheUnitedStates(20–40%).NortheasternChinaisthenetdischargesourceofCO2,mainlyresultedfromtheexcessivedeforestationandthedegradationofforest.Andmorethan65%ofcarbonsequestrationisinSouthernChinabecauseofregionalclimatechange,plantingandtherecoveryofshrubs.Themechanismandthereasonofclimatechangeresearchhasalwaysbeenthedifficultiesandfocusoftheclimatechangeresearch,andtheuncertaintyofresearchalsohasattractedmuchattention.Geetal.(2010a,b)analyzedtheuncertaintyoftheresultoftheexistingclimatechangeresearches,includingthestatesofclimatechangeinpasttwothousandsyears;forexample,istherethemedievalwarmperiodandlittleiceage?Isthe20thcenturythewarmestperiodinthepastthousandyears?Didthewarmingtrendstop?Greenhouseeffect(thedifferentunderstandingaboutthegreenhouseeffectmechanism,therelationshipbetweengreenhousegasdis-chargesandthetemperaturevariation,theeffectofwatervaportothegreenhouseeffectandwarming);climatemodelsimulation(thecomparisonofsimulationandmeasuredresults,thedefectsofthemodel)and2°Cthresholdandsoon(itssourceandphysicalsignificance;thedifferentunderstandingsof2°Cthreshold).Finally,itisconfirmedthatthedivergenceandheateddebateaboutclimatechangeisinevi-tableduetothecomplexityoftheclimatechanges.Manycurrentstudiesontheclimatechangesarenotconclusiveandmanyproblemsneedtobefurtherstudied.Zhao(2006)alsobelievesthatthedifficultiesoftheprojectionofclimateeventsin 201Introductionfutureonehundredyearsarehowtoestimatethereliabilityandtheuncertaintyoftheglobalclimatechanges,howtoconsiderthecombinedeffectofbothnatureandhumanandhowtoreducetheuncertaintyofprojection.Fang(2011)thinksthatitisarealitythattheclimateischangingandtheearthiswarming,butthereasonsofclimatechangearequitecomplexandhavenotyetbeendeterminedatpresent.1.2.3TheImpactofClimateChangeClimatechangehasbroughtsomeconsequencestonatureandeconomicsociety,suchas,moreandmoreextremeweatherandclimateevents,increasingproductioninstability,worseningproblemofthewaterresources,significantretreatofglacier,thegreaterriskofmajorengineeringsecurity,thethreatofsealevelrisetothedevelopedcoastalareas,thedestructionofbiodiversityandsoon.Inaddition,climatechangewillproducemoreeffectsonhumanhealth,industry,tourism,politics,economyanddiplomacy.Lietal.(2003a,b,c)thoughttheimpactsofclimatechangemainlyreflectonthechangeofclimaticzone,theimpactonwaterresources,thechangeofnaturalbelt,sealevelrise,increasingnaturaldisasters,theimpactonagriculture,theinfluenceonengineeringandconstructionandtheincreaseofplantdiseasesandinsectpests.TheobservationalstudiesconfirmedthatthenorthernboundarybetweensubtropicsandtemperatezoneinEasternChinamovetowardsnorthandthephenologicalperiodhasbeenmovedup.Inthepastfewdecades,theforestareainQilianMountainreduced16.5%;thelowertreelinerosefrom1,900to2,300mandthecoveragedecreased10%.Since1980s,degradationofgrasslandecosystemintheriverheadareasoccurred,andthewetlandinSanjiangPlainreduced.Thenorthernboundariesofeachclimaticzonewillcontinuetomovetowardsnorthalongwiththeglobalwarming.Theextentofdroughtmaybeexpanded,butthewetnessareamaybenarrowed,andtheNorthernChinatendstoaridification.WiththeThevegetationzonesofforestmovingtowardsnorth,theproductivityandpro-ductionoftheforestwillhavedifferentdegreesofincrease,butthefrequencyoffiredisasterincreasesandthespreadscopeoftheforestdiseasesandinsectpestswillexpandandaggravate.ThealpinegrasslandareasofQinghai-Xizangplateauwillreducesignificantlyandthedesertinplateaumountainwillincrease.TheoutputandqualityofgrasslandinSichuanprovincedropslightlyandthewetlandareasinSouthwesternChinareduce,eventhewetlandfunctionofSanjiangPlainandQinghaideclines(CountryAssessmentofClimateChanges2007).Since1950s,themeasuredrunoffofsomeriversisonthedecline,suchastheYangtzeRiver,theYellowRiver,thePearlRiver,theSonghuaRiver,theHaiheRiver,HuaiheRiverandsoon.From1990s,thedroughtinthenorthandfloodsinthesoutharefrequent,whichcausealotofpropertylosses.Sincethe20thcentury,China’smountainglaciersretreatgenerallyandtheglacierareainthewesternmountaindecreased21%.Inthenext50–100years,themeanannualrunoffdepthinsomeprovincesofNorthernChinawilldecrease2–10%,butthemeanmag-nitudeofrunoffreaches24%,whichresultsinthewatershortagesofthenorth 1.2AdvancesinClimateChangeResearch21areasandfurtheraggravationoffloodinsouthareas.By2050,theglacierareainthewesternareasis27.2%lessthanthemiddleofthe20thcentury,amongthereductionofoceanicglacierismostsignificant.ThegreatreductionoficereservesinWesternChinaandthemountainousareasmaketheseasonaladjustmentoftherunoffreduce(Zhangetal.2008a,b).Theinfluencesofclimatechangetowatercycleincoldareasaredisplayedbyprecipitation,evaporation,runoff,snowarea,glacierandpermafrost.TheevaporationoftheNorthernHemispherehasbeengraduallyreducingandtherunoffanditsspace-timedistributionhavetakenplacegreatchanges.Thesnowcoverareaissmallerandsmallerandtheglacierisshrinkingquickly.Alongwithetheglobalwarming,permafrostmeltleadstothethicknessoftheactivelayerincrease.Theabovechangesbringtheaccelerationoftheglobalwatercycletoagreatextent(Shaoetal.2008).ClimatewarmingwillcausesealevelriseandtheinundationareaofcoastallowlandwillexpandinChina.Theseareaswillbethreatenedseriously,includingtheYellowRiverdelta,theYangtzeriverdeltaandthePearlRiverDelta.Ifsealevelrise30cm,theinundationareawouldbe0.81and0.23%ofChinainthecontextofnon-fortificationorcurrentfortification.Itwasstudiedthataccordingtothefutureclimatesituation,thedroughtintheupperreachesofYangtzeRiverwillbemitigated;thefrequencyoffloodingwillincreaseinfloodseasons,whichincreasethepossibilityofdebrisflowandlandslide(Zhangetal.2000).Asthetemperaturesrise,thepermafrostintheQinghai-XizangPlateauisgraduallydegrading.Upto2050,80–90%ofthepatchypermafrostwouldhavedegraded;theseasonallythaweddepthwouldincrease;andpermafrostareainthesurfacewouldreduce10–15%.TheriseoflowerboundaryofpermafrostwillaffectthestabilityofQinghai-Xizangrailwayroadbed.Inaddition,fortheclimatechanges,thereisagreatinfluencetothewaterqualityoftheeastlineofproject,ratherthanSouthtoNorthWaterTransferProject(CountryAssessmentofClimateChanges2007).Withthefrequencyofextremeweatherincreasing,allkindsofweathersystemactivitieswillbemoreintenseandfrequent.Forexample,thefrequencyofmete-orologicaldisasterswillincrease,suchas,drought,floods,hightemperature,chillingdamageandsoon,whichwilladdtothevolatilityoftheagriculturalproductionandtheagriculturallosses.Temperatureincreasehascertainpositiveeffecttothecropyieldsinsomeareasbutthesignificantnegativeeffectsonthewhole,meanwhile,theyieldandqualityofthemaincropdeclinefurther.Asthetemperaturerise,destructiveinsectswillgrowupinadvanceandtoomuchbreedinginayear,leadingtothemuchhazardofcrops.Theburstsizeofavailablenitrogenistoincreasewiththeclimatewarming.Ifitissupposedtokeepthesoilfertileasitwas,thefertilizerratemustbeincreasedresultinginthemoreproductioncostandmorehazardofsoilandenvironment.By2030,China’stotalgrainproductionwilldecrease5–10%,forexample,thethreemaincropsincludingwheat,riceandcorn(NingandShen2009).Additionally,Easterlingetal.(2000)summedupthatfre-quentextremeweathereventsaddtheprobabilityofvariouskindsofnaturaldisasterscausingseriouslossestothedevelopmentofsocialeconomy,especiallythefrequentoccurrenceofextremeweatherevents.Forexample,theeconomiclossesoftheUnitedStateshasreachedto6billionsdollarsin1990sfrom100 221Introductionmillionsdollarsin1960sbecauseofthestorms,andthenumberoftimeshasincreasedby35timesin1990sfrom10timesin1960s.Besides,thelosscausedbyhurricanehasrisenfrom5billionsdollarsinthe1940sto40billionsdollarsin1990s(ChapmanandWalsh1993).Theimpactsofclimatechangeondesertificationarereflectedinthescope,theoutstretchedvelocity,theintensityandthepotentialriskofthedesertification,aswellasthestructure,thefunctionandtheproductivityofthearidecosystem.Meanwhile,astheimportantstorageofcarbonintheworld,thechangeofaridzone,tosomeextent,affectstheincreaseanddecreaseofCO2intheatmosphere.Itwasestimatedthattheamountofcarbonlossresultedfromglobaldesertificationwilltotaled18–28PgC(CiandYang2004).Overthepast50years,thesignificantwarmingoccurredintheNorthernChinaandthethermalresourcesincreasedinthegrowingseason.Theavailablewaterandsunshineshowedreducingtrendsindif-ferentdegreesandweredistributedunevenlyintimeandspace.Theagrometeo-rologicaldisasterslikefrostdamage,chillinginjury,coldwave,floods,hailandsomedecreasedfollowedbytheincreasingdrought.Theclimatechangeofthenortheasternareasgenerallybenefittheagriculture,displayedbytheextendedgrowthperiodofcrops,theaccelerateddevelopmentprocessandtheshortenedgrowthperiod.Theaccumulatedtemperatureincreaseobviously,atthesametime,itmovenorthwardandenlargeeastward,whichmaketheplantingareaexpanded(Zhao2010).Basedonthestudyofclimatechange,therearesomeadvantagesanddisadvantagestothesouthwesterntourismresources.Theadvantagescanbeshownthattheperiodoftourismwilllengtheninordertopromotetheeconomicdevel-opmentoftourisminthisdistrictduetotheriseofthecomfortdegreeoftem-perature.Asweallknow,theSouthernChinaisknownasa“genepoolofnaturalplants”and“kingdomofanimals”.However,thethreatofclimatechangesisfataltothespeciesdiversityinSouthernChina.Thelossofspeciesdiversitywillbringtheenvironmentaldegradationandhaveanegativeimpactontourismimage,thusthetourismincomealsowillreduceinacertainextent.Thisisthedisadvantagesofclimatechangetothesouthwesterntourismresources(Yangetal.2006).Underthebackgroundofthetemperaturerise,thespringphenologyofwoodyplantsinChinabeforeandafter1980shasobviouschanges,whichisconsistentwiththetrendoftemperaturevariationinspring.Themovementofthephenologicalperiodchangesmallerbecausethemagnitudeofspringwarminginnorthernareasisquitebigratherthanthesmallermagnitudeinsouthernareas(Zhengetal.2003).However,justasthethoughtofFang(2011),theimpactsofclimatechangeonthenaturalandsocialsystemarestilldisputedbyscholarsandneedtoobjectivelyandrationallybeknownbecausetheimpactshavebothadvantagesanddisadvantages.Theresearchofhumancivilizationindicatesthatthegreatprogresseshavealwaysbeenmadeinthewarmperiodofearth,butthedeclineofacivilizationwasaccompaniedbythecoldnessallthetime.Inrecent70years,humansocialproductiveforceshasaremarkableincreaseandthematerialcivilizationalsomakesanunprecedented.Although,itislikelytobeahistoricalcoincidence,itisthematerialbasisofthedevelopmentofhumancivilizationandalsoanundeniablefactthatthewarmingclimateishelpfultoincreasethecropyield. 1.2AdvancesinClimateChangeResearch231.2.4TheCurrentCharacteristicsoftheClimateChangeResearch(1)Fundamantality.Thestudyonthechangeprocessoftheclimatesystemisstillthemaindirectionofclimatechangeresearchandisalsothefundamantalityofcomprehensivelyandsystematicallyrecognizingtheclimatechange.Theconfirmationoftheclimatechangemechanismisstillthethemeofcurrentclimatechange.Becauseofthecomplexityoftheprocessofclimatechange,therearesomelacksontheunderstandingofthedrivingmechanisminclimatechangeondifferenttimescales.Theuncertaintyevaluationofprocess,mechanismandpredictionofclimatechangeisstilladifficultyofclimatechangeresearch.Nowtherearelotsofscientificuncertaintyonunderstandingofthemechanismofclimatechange,particularlyinthousandyearsscales.SoThereisstillalongwaytosystematicallyawaremanykeymechanismsandprocesses.Theforecastoffutureclimatechangehasbeenthedifficultyofclimatechangeresearch,andthereisabigchallengeontheerroranalysisanduncertainassessmentofthefruit.Theclimaticandenvironmentaleffectsofcryospherechangeshavedrawnmoreattentionandhavegraduallybeenanewconcernbecauseofitssensitiveresponseandfeedbacktoclimatechanges,buttheawarenessofitsclimatic,hydrologicalandecologicaleffectsisstillverysuperficial.Althoughtheassessmentoftheeffectsofclimatechangehasbecomeincreasinglymature,therearesomeshortcomingsonthestudyofmitigationandadaptationstrategies.(2)Spanning.Theclimatechangeresearchhasshiftedfromthesingleresearchoftheairtemperatureandprecipitationtothecomprehensiveanalysisofchangesintheclimatesystem,suchasextremeweatherevents,windspeed,sunshine,cloudcover,thepotentialevaporationandsoon.Thiscomprehensivestudyontheclimatesystemisnotonlyhelpfultosystematicallyunderstandthematterofclimatechange,butalsotofurtherawarethemechanismofclimatechange,whichwilllaythephysicalfoundationforthepredictionsforthefutureclimatechange.Theanalysisofthefactandprocessofclimatechangeshastransferredtothecognitionofthemechanismanddrivingforce.Generallyspeaking,thedominantcauseoftheclimatechangeisthechangeoftheglobalradiationbalanceandtheoscillationoftheclimatesystemitself.Inotherwords,theclimatechangehasitsphysicalbasis.Sobasedonthephysicalbasis,theresearchonthemechanismofclimatechangebecomeanimportantaspectoftheclimatechangeresearch.Althoughtherearemuchcontroversyontheunderstandingofmechanismofclimatechangeinhundredyearsscales,thecomplexity,comprehensivenessandnonhomogeneityofmechanismoftheclimatechangeareconfirmedonceagain,whichlaythefoundationforthebreakthroughresearchofthenewmechanismandpointoutthedirection.Thepredictionresearchofcurrentclimatechangelaysstressonthecoupledpro-cessofthemultipleforcingfactors,whichrequiresmoreexplorationstocoupledmechanism.Forexample,takingthechangeoflanduse,vegetation 241Introductioncoverchangesandatmosphericaerosolintoconsideration.While,thefutureforecastsresearchneedacomprehensiveconsiderationbyputtingapositiveforceandanegativeforceintothesameenvironment.Theresearcheshavetransferredfromknowclimatechangetoadapttoit.Theclimatechangeisaneternaltheme.Atpresent,scholarshavepaidmoreattentiontothecopingstrategiesafterclimatechange,namelyhowtoslowdownandeventuallyadapttothevariouseffectsbroughtbytheclimatechangeinordertorealizethesustainabledevelopmentofhumansociety.Currently,oneofthemostcontroversialissuesfocusonwhetherthedriveofclimatechangeisnaturalorhuman,whichwillraiseawarenessofclimatechangetoalargeextentandprovideanewtrainofthoughtforamorecomprehensiveunderstandingofthemechanismofclimatechange.Thisunderstandingwillfurtherpromoteamajorbreakthroughinthemechanismofclimatechangeresearch.(3)Comprehensiveness.Thecurrentresearchofclimatechangehighlightsthecomprehensiveutilizationofvariousmeans,whichprovidesabettertechnicalmeansforthedevelopmentoftheclimatechangeresearch.Atpresent,therecordofclimatechangeresearchhasconvertedfromsingletomultipleinordertofindoutthesimilarityofchanges.Thisconversionimprovesthescientificlevelandcredibilityoftheclimatechangeresearchtoalargeextent.Thecooperationandcommunionofmoredifferentresearchescanalsomakethereliabilityandcredibilityoftheclimatechangeresearchgraduallyincrease.Mechanismresearchisacomprehensiveanalysisofearthgiantsystem,therefore,thecrosswithothernaturalsciencesisthekeybasisofthisresearch.Inaddition,thecrosswithsocialscienceoutstandsthestudyoncounter-measuresresearch.Inthefinalanalysis,theadaptationofclimatechangeiswhatscientificandreasonablemeasuresshouldbetakenwhenthegiantsocietyasthemainbodyofhumanbeingfacetheproblemofclimatechange.Sointhecontextofthis,ontheonehand,itisnecessarytoreducetheimpactofclimatechangetous;ontheotherhand,weshouldfinallyadapttothenewclimatethroughthescientificandrationalresponse.(4)Sensitivity.Climatechangeisnotonlyanenvironmentalissues,butalsoadevelopmentissue,inthefinalanalysisitisthedevelopmentissue.Climatechangeresearchisrelatedtonationalsurvivalanddevelopment,andisthehotfieldoftoday’sinternationalscientificresearch.Especiallyinthe15thcon-ferenceof“UnitedNationsFrameworkConventiononClimateChange”(UNFCCC)in2009inCopenhagen,thedevelopedcountriesagaintakinguseoftheshiftfromtheunderstandingofclimatechangeintoapoliticalconsensuswritetheknowledge,“globaltemperatureriseshouldbelimitedwithin2°C”withagreatcontroversyinscienceintothe“CopenhagenAgreement”inordertolayavitalfoundationfortheimplementationofaseriesofstrategies,thepurposeofwhichistolimitthedevelopmentofdevelopingcountries.Underthebackgroundofthis,thestudyonthecarboncycleandtheinfluenceofnaturalandhumanfactorstothetemperaturerisehavebeenanewhotspotintheresearchesoftheclimatechange.Atthesametime,theconcepts,suchaslowcarboneconomy,greeneconomy,environmentalprotection,mitigation 1.2AdvancesinClimateChangeResearch25andadaptationofclimatechange,carbonreductionandsomegraduallybecomethenewconsciousnessofsocialdevelopment.While,thedevelopedcountriescombinecarbondischargesandtherightofdevelopmentthroughtheirpoliticalinfluence,andbringalotofpressuretothedevelopingcountriesortheemergingindustrializedcountriesbyvariousmeans,forexample,theinternationalclimatenegotiations.Zheng(2010),thedirectoroftheChinaMeteorologicalAdministration,thoughtthatChina’sresponseonclimatechangeaftertheCopenhagenclimateconferenceshouldfocusonthefol-lowingaspects:Thecopingworksshouldbeputintothelegalsystem;Itisnecessarytodevelopandpromotetheenvironment-friendlytechnologiesandtodevelopthelowcarboneconomy,greeneconomyandcirculareconomy;Itshouldbedonetostrengthentheinfrastructureoftheweakareasandtoimprovethecomprehensiveabilityofadaptingtoclimatechange;WeshouldactivelyexplorethemarketsystemandmechanismconformedtoChina’snationalconditions;Weshouldstrengthenthescientificresearchandtech-nologicaldevelopmentofclimatechangeandimprovethesoftpowerofsci-enceandtechnology;Weshouldenhancetheconsciousnessofrespondingclimatechangeinthewholesociety;Wealsoshouldstrengthentheknowledgepopularizationofclimatechangeandenhancesociety’sawarenessoftheimportanceandurgencytotackleclimatechange.1.3TheMainContentsOnthebasisofexistingresearch,bycollectingandsortingthemeteorologicaldata,NCEP/NCARreanalysisdataandtheglacierchangedatafromthesurface-basedobservingstationsthisstudyfocusestheanalysisonthecharacteristicsofthespatialandtemporalvariationsofclimatefactorsinSouthwesternChina,exploresthepossibleinfluencingfactorsandanalyzestheresponseoftheglaciersystemtoclimatechange.Themaincontentsofthisstudycanbedisplayedasfollows:(1)Thisstudyutilizesavarietyofdatatoanalyzethespatiotemporalcharacter-isticsofannualandseasonalmeantemperatureandprecipitation.Basedontheanalysisofsealevelpressure,geopotentialheightandwindfieldetc.,thisstudyprobesintotheatmosphericcirculationmechanismofresearchedareasandfurtheranalyzestheinfluencesofelevationonairtemperatureandpre-cipitationvariations,thedifferencesofchangetrendsbetweentheurbanandtherural,therelationshipofairtemperaturevariationswithradiation,seasurfacetemperature(SST)andsunshinedurationandsoon,andtheeffectsofthewatervaporfluxandthewesternPacificsubtropicalhighontheprecipi-tationvariation.(2)Byusingthelatestinternationaldefinitionofextremetemperatureandrainfallevents,statisticalmethodandthestandardofextremethresholdvalue,weconducttheresearchonthespatialandtemporalvariationsandtheinfluencesof 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Chapter2DataandMethods2.1Data2.1.1TheObservationData2.1.1.1TheObservationDataofSouthwesternAreasfromChinaMeteorologicalAdministrationTheobservationdataofgroundstationsisthemaindatasourceofthisstudy.Thedataaboutthedailymeantemperature,dailyminimumtemperature,dailyprecip-itation,dailywindspeedanddailysunshinehoursarefromthemeteorologicalobservationdatabaseofnationalmeteorologicalinformationcenterinChinaMeteorologicalAdministration(http://www.nmic.gov.cn/).ThetimespanofmeteorologicaldataismainlysetfromJanuary1st,1961toDecember31st,2008inordertoensurethelengthofalldatauniformandstable.It’simportanttonotethatthewindspeeddataexistdiscontinuityintherecordbecauseofthereplacementofthemonitoringdevicein1960s(Liuetal.2004).Forthesakeofavoidingthisproblem,thisstudyselecttheperiodfromJanuary1st,1969toDecember31st,2008tostudybaseontheselectionofXuetal.(2006)aboutthestudyperiodofthewindspeedchangeresearchinChina.WegatheredallgroundobservationdataintheadministrativerangeoffiveprovincesinSouthwesternChina.There27stationsareeliminatedduetosomereasons,suchas,newstations,alongerbreakduringobservation,theproblemindatarecordsandqualityandsoon.Therestofthemeteorologicalstationsspacedistributeunevenly,especiallytherearefewstationsinthewestoftheXizanganPlateau.Wewipeonemoreoff(Shiquanriverstation)inordertoreducetheimpactofsparsestationstoclimatechangeinthewholearea.Finally,110meteorologicalstationsareremained,whichhavethedataofgoodquality,relativelyevendistributionandrelativelycontinuousrecordsandwhicharebuiltearlierthan1961(Fig.1.1).Theworldmeteorologicalorganization(WMO)number,thename,longitude,latitude,altitude,etc.ofstationsselectedinthis©Springer-VerlagBerlinHeidelberg201537Z.Li,StudyonClimateChangeinSouthwesternChina,SpringerTheses,DOI10.1007/978-3-662-44742-0_2 382DataandMethodschaptercanbeseeminTable2.1.Theelevationrangeofthis110stationsisbetween285.7and4,700m.Amongthem,thereare9stationsareabove4,000m;theelevationrangeof17stationsisbetween3,000and4,000m;theelevationrangeof16stationsisbetween2,000and3,000m;thereare32stationslocatedin1,000–2,000mandthereare36stationslocatedin1,000mbelow.TherelateddataoftheEastAsianmonsoonindexandSouthAsiamonsoonindexin1961–2001usestheresearchachievementsofGuoetal.(2004)forreferences,andthedataofplateaumonsoonindexisprovidedbyChinaMeteorologicalAdministrationNationalClimateCenter(http://ncc.cma.gov.cn/cn/).Inaddition,thepopulationandenergyconsumptiondatainChinaarefromtheprovincialstatisticalyearbook.2.1.1.2TheDataQualityControlofStationsMoststationsinChinawasestablishedinthe1950s,andthestationobservationdataismoresteadyafter1960s.However,stations’move,environmentchangearoundstations,thetypesofobservationinstrumentandthechangeofobservationtimeallwilldirectlyaffectthecomparativenessandcontinuityoftheobservationrecords,andhavethedifferentdegreesofinfluenceontheuniformityofannualclimatedatasequence(Wu2005).Inaddition,thereabout70%ofChina’s731standardgroundobservationstationshaveexperiencedrelocation,ofwhichabout31%moveonceandabout41%movemorethantwotimes,especiallythestationslocatedinthecity,forexample,thestationsinBeijing,Shanghaiandothermajorcitieshavemovedtothedistrictbetweensuburbsandcities(Lietal.2004a,b).Soitisnecessarytoselectqualifiedobservationdatabythedataqualitycontrolbeforeanalysisinordertoensuretheaccuracyoftheresultsofthestudy.Thequalitycontrolofmeteorologicalobservationdatainthisstudyistoexaminethedateofthedailymeantemperature,dailyminimumtemperature,dailymaximumtemperatureanddailyprecipitationbyusingtheinternationaltestmethodandsoftwarenon-uniformity:RclimDexandRHtest,andtofindoutthestationhavingdataqualityproblems,thentodeletethemfromtheoriginaldata,finallytoselectthequalifiedobservationstationsandtomakeastatisticsandanalysisonthebasisofthisdata.Thecontrolandinspectionofdataqualitymainlyincludesthreeaspects:whethertherecordingdateofdataisconsistentwithreality;whetherthedailyprecipitationislessthanzeroandwhetherthedailyminimumtemperatureisgreaterthanthemaximumtemperature;whethertherelocationandthelocalenvironmentchangescausedtheoftheobservationdatarecords.DataqualitycontrolmainlyuseRClimDexsoftwareandthetextofdatanon-uniformityuseRHtestsoftware.Thesoftwaresaboveandtheirdocumentationcanbedownloadedinthiswebsite(http://cccma.seos.uvic.ca/ETCCDI/software.shtml)thereadingfileandwritingfileofsoftwaresabovehavetheirspecificformats.Itisthefirststepoftextingthequalitycontroltopreparethedataformatasrequired.Therearefiverequirementsintheinputofsoftwaresabove.Firstly,thedatafilesshouldbeASCIItextfiles.Secondly,thedatasequencemaybetheannual,monthlyanddailyprecipitation,theminimumtemperature,themaximumtemperature(the 2.1Data39Table2.1TheselectedweatherstationsinSouthwesternChinaWMOnumberNameLatitudeLongitudeAltitude(m)55279Bangor31°23′90°01′4,70055299Naqu31°29′92°04′4,50755472Xainza30°57′88°38′4,67255578Shigatse29°15′88°53′3,83655591Lhasa29°40′91°08′3,648.955598Tsetang29°15′91°46′3,551.755664Dingri28°38′87°05′4,30055680Jiangzi28°55′89°36′4,04055696Longzi28°25′92°28′3,86055773Parry27°44′89°05′4,30056312Nyingchi29°40′94°20′2991.856106Suoxian31°53′93°47′4,022.856116Dingqing31°25′95°36′3,873.156137Chamdo31°09′97°10′3,30656227Bowo29°52′95°46′2,73656038Shiqu32°59′98°06′4,20056079Ruoergai33°35′102°58′3,439.656144Derge31°48′98°35′3,18456146Ganzi31°37′100°00′3,393.556152Sertar32°17′100°20′3,893.956167Daohu30°59′101°07′2,957.256172Barkam31°54′102°14′2,664.456173Hongyuan32°48′102°33′3,491.656178Xiaojin31°00′102°21′2,369.256182Songpan32°39′103°34′2,850.756187Gaoping30°49′106°15′30056188Dujiangyan31°00′103°40′698.556193Pingwu32°25′104°31′893.256196Mianyang31°27′104°44′522.756247Batang30°00′99°06′2,589.256251Xinlong30°56′100°19′3,00056257Litang30°00′100°16′3,948.956287Ya’an29°59′103°00′627.656357Daocheng29°03′100°18′3,727.756374Kangting30°03′101°58′2,615.756385Emeishan29°31′103°20′3,047.456386Leshan29°34′103°45′424.256441Derong28°43′99°17′2,422.956459Muli27°56′101°16′2,426.556462Jiulong29°00′101°30′2,987.3(continued) 402DataandMethodsTable2.1(continued)WMOnumberNameLatitudeLongitudeAltitude(m)56475Yuexi28°39′102°31′1,659.556479Zhaojue28°00′102°51′2,132.456485Leibo28°16′103°35′1,255.856492Yibin28°48′104°36′340.856671Huili26°39′102°15′1,787.357206Guangyuan32°26′105°51′513.857237Wanyuan32°04′108°02′67457306LangZhong31°35′105°58′382.657313Bazhong31°52′106°46′417.757328Daxian31°12′107°30′344.956565YanYuan27°26′101°31′2,54557405Suining30°30′105°33′35557608XuYong28°10′105°26′377.556571Xichang27°54′102°16′1,590.956586Zhaotong27°21′103°43′1,949.556651Lijing26°52′100°13′2,392.456664Huaping26°38′101°16′1,244.856444Deqin28°29′98°55′3,31956684Huize26°25′103°17′2,110.556739Tengchong25°01′98°30′1,654.656748Baoshan25°07′99°11′1,652.256751Dali25°42′100°11′1,990.556763Yuanmou25°44′101°52′1,120.656533Gongshan27°45′98°40′1,583.356543Zhongdian27°50′99°42′3,276.756548Weixi27°10′99°17′2,326.156768Chuxiong25°02′101°33′1,824.156778Kunming25°00′102°39′1,886.556786Zhanyi25°35′103°50′1,898.756838Ruili24°01′97°51′776.656856Jingdong24°28′100°52′1,162.356875Yuxi24°20′102°33′1,716.956880Yiliang24°55′103°10′1,532.156886Luxi24°32′103°46′1,704.356951Lincang23°53′100°05′1,502.456954Lancang2°34′99°56′1,054.856959Jinghong22°00′100°47′58256964Simao22°47′100°58′1,302.156966Yuanjiang23°36′101°59′400.956969Mengla21°29′101°34′631.9(continued) 2.1Data41Table2.1(continued)WMOnumberNameLatitudeLongitudeAltitude(m)56977Jiangcheng22°35′101°51′1,120.556985Mengzi23°23′103°23′1,300.756986Pingbian22°59′103°41′1,414.156994Wenshan23°23′104°15′1,271.659007Guangnan23°29′104°31′1,227.557348Fengjie31°01′109°32′299.857633Qiuyang28°50′108°46′664.157426Liangping30°41′107°48′454.557432Wanxian30°46′108°24′186.757516Shapingba29°35′106°28′259.157522Fuling29°45′107°25′273.557606Tongzi28°08′106°50′97256691Xianning26°52′104°17′2,237.556793Panxian25°43′104°28′1,80057614Xishui28°20′106°13′1,180.257707Bijie27°18′105°17′1,510.657713Zunyi27°42′106°53′843.957722Meitan27°46′107°28′792.257731Sinan27°57′108°15′416.357741Tongren27°43′109°11′279.757803Qianxi27°02′106°01′1,231.457806Anshun26°15′105°54′1,431.157816Guiyang26°35′106°44′1,223.857825Kaili26°36′107°59′720.357832Sanhui26°58′108°40′626.957902Xingren25°26′105°11′1,378.557906Wangmo25°11′106°05′566.857916Luodian25°26′106°46′440.357922Dushan25°50′107°33′1,013.357932Rongjiang25°58′108°32′285.7unitofprecipitationismm,andtheunitoftemperatureis°C).Thirdly,thereshouldhavespacesbetweenthedatacolumns.Forexample,eachelementisseparatedbyoneormorespace.Fourthly,thelostormissingdataintherecordsmustbetakenplaceby−99.9coding.Fifthly,thedatarecordsmustbeorderedasthecalendardate.RClimDexsoftwaremainlyincludesthreestepstodothequalitycontrol:(1)tomodifyallthemissingvaluestotheformatwhichcanbeidentifiedbysoftware,forexample,−99.9,afterautomaticallyidentifyingtheerroroftherawdataandtoreplaceallunreasonablevaluetoNA(notavailable),forexample,negativerainfall 422DataandMethodsorlessdailymaximumtemperaturevaluethanthedailyminimumtemperature.(2)Toexaminethepotentialoutliersinthedatasequencesothattheresearchersmakeatest,calibrationanddeleteaccordingtotheactualdata.Theoutliersreferstothevaluesthatthedailydatarecordsaremorethanusercustomrange.Meanwhile,theresearchersthemselvescansetthethresholdofoutliersaccordingtotheactualsituationoftheselecteddata.Generally,therecordrangeofthedataisdefinedasadailymeanvalueplusesorminusesthentimesstandarddeviation,thatis(mean−n*std,mean+n*std).Amongthem,stdpresentstheintradaystandarddeviation;nisthethresholdofoutliersinputtedbyusers,forexample,thedailymaximumtemperatureis30°C.Inthisstudy,thethresholdofoutliersissetasthedailyhighesttemperatureisnotmorethan45°C,thedailyminimumtemperatureisnolessthan−35°C,andthedailyrainfallisnotmorethan180mm.Inthiscaseofthis,thestudysetthreestandarddeviationtotestthethresholdofabnormaldatasoastobetterdeterminethequalityoftherawdata.(3)Thesoftwarewillautomati-callygeneratetimeseriesdiagramsrainfallandtemperatureinordertocheckwhetherthereisanyqualityproblemintheinterannualandin-yearchangeofdata(Aguilaretal.2005;Newetal.2006).Forexample,Fig.2.1isanexampleofqualitycontrolofprecipitationdata.WhetherthereisanyqualityproblemintheprecipitationdatabythegeneratinghistogramandtheKernelfilteringisodense,whichisakindofnonparametrictestmethod(Aguilaretal.2005).Theprecipi-tationdataqualityshowedbythisfigureisgood.Figure2.2isthetrenddiagramofin-yearchangeofprecipitationandtemperatureautomaticallygeneratedbyRClimDex.Throughthisfiguretheoutliersoftemperatureorprecipitationfromacertainstationcanbemonitored.Figure2.3istheinter-annualvariationofDTRrecordedbyRClimDex,whichisusedtotesttheabnormalsituationinitschangingtrend.TheuniformitytestofdataisrelativelycomplicatedandusuallyneedtodowiththeaidofthedetailedrecordsofinspectedstationsandtherecordsofthenearbyFig.2.1Exampleofdailyprecipitationsuccessfulqualitycontrolproceduresusing.RClimDex(Histogram(verticalbars)andKernel-filtereddensity(line)showingthehighdensity) 2.1Data43Fig.2.2AnnualvariationofdailyprecipitationandthemaximumtemperaturerecordedbyRclimDexduring1980–1989Fig.2.3Inter-annualvariationofDTRinAnshunstationrecordedbyRClimDexstations(Dyurgerov2003).AtpresentinChina,therearenonuniformityintheclimatedatasequenceduetothehistoricalevolutionofthemeteorologicalstations,especiallyrelocationofthesite.Andtheinspectionworkofnonuniformityisstillnotenough.Manyresearcherslackenoughawarenesstotheimportanceand 442DataandMethodsapplicationvalueoftheinformationabouthistoricalevolution,andmostoftheresearchworkbyusingthedataofstationsalllaketheanalysisandtestoftheannualdatasequence(Wu2005).Inthisstudy,wechooseRHtesttoevaluatetheuniformityofobservationdatafrommeteorologicalstations,whichestimatethemultiplestepchangeexistinginthetimeseriesofdatabasedonthetwophaseregressionmodel(Wang2001;WangandZhou2005).Forthefirsttime,EasterlingandPeterson(1995)usedRHtesttoexaminethenonuniformityofthetimeseriesofdatainthestudyofCanadianclimateextreme.LundandReeves(2002),Wang(2003)madethefurtherrevisionthroughtheirownresearches.Zhangetal.(2004)examinedthedailymaximumtemperature,dailyminimumtemperatureandannualchangetrendofdailyrangebyusingtherevisedtwophaseregressionmodel,identifiedthepotentialnonuniformityofdataandobtainedgoodstudyeffect.Thereafter,thismethodgetsagreatacademicrecog-nitionasoneoftheimportantmethodsoftestingnonuniformityofdatasequence,haseventuallybecomeavisualizationsoftwareavailableforusersandhasbroughtgreatconvenienceforscientificresearchworkers.Thefirststepofthismethodistotesttheannualsequencechangesofthedatabytheanalysisofregressionmodel.Thesecondstepistouseregressionmodeltofindoutthediscontinuityinannualsequencechanges.ThethirdstepistoapplyFtesttodeterminethestatisticalmeaningoftheregressionmodel.Onlywhentestresultsoftheregressionmodelinthefirststepwouldhavereachedtheconfidencelevelof95%,theresultsoftheregressionmodelinthesecondstepwasbelievedtobereliable.Thefourthstepistoidentifywhetherthediscontinuouspointshavestatisticalmeaningandtofinalizetheuniformityofthedatasequence.Thedatasetselectedinthisstudyhaveeightstationsexistingpotentialdiscontinuityinthesequenceofdailymaximumtem-peratureandfourstationsinasequenceofdailyminimumtemperature(Fig.2.4).Throughseekingtheoriginalrecordsofdataandthehistoricaldocumentsofstations,wefoundthatonlyoneappearsdiscontinuityofdatabecauseofsiterelocationamongthe12stations,thediscontinuousdataoftherestiscausedbyoutliers.Hereby,weeliminatetheseoutliersandremoveastationwithdatanonuniformity,inwhichthedailymeantemperature,dailymaximumtemperatureanddailyminimumtemperatureshasthediscontinuityaround1983andthetemperaturevariationcharacteristicsissignificantlyconsistentwiththataroundthestations.Wefoundthestationsiterelocatedin1983aftercheckingthedatarecords.Throughaseriesofprocedures,wefinallyselect110eligiblestationstobeusedinthisstudy(Table2.1).2.1.2TheDataonGlacierChangeThedataabouttheterminusfluctuationofglaciers,thechangeinareasandicelake,materialbalanceandsofortharemainlyfrompreviousworks,thedetailsofwhichcanbeshowninChap.7.Herewewillfocusonthesourceofdataontheterminusfluctuationofeightglaciers,suchasHailuogouGlacier,HailuogouNo.2Glacier,Big 2.1Data45Fig.2.4Homogeneitytestofannualmeandailymaximumtemperature(a),minimumtemperature(b),andmeantemperature(c)forstationJiali(30°40′N,93°17′E,4,488.8ma.s.l.).(Thelargest,statisticallysignificantdiscontinuityaround1983isverifiedbytheoriginalstationdata,whichindicatethatthestationrelocatedin1983)GongbaGlacier,SmallGongbaGlacier,MingyongGlacier,AzaGlacier,YanzigouGlacierandBaishuiNo.1Glacier.Before1997,thedataabouttheterminusfluc-tuationoftheseglacierswerefrompreviousstudies(Heim1936;Suetal.2002;Zhangetal.2001;Pu1994;Liu2005;Lietal.2008,2009a,b,2010a,b).ThedataofHailuogouGlacierin2006andthedataofBigGongbaGlacierandSmallGongbaGlacierin2007arefromauthor’son-the-spotinvestigationin2006and2007;andsince1997,thedataofBaishuiNo.1GlacierarefromthefieldobservationsofMountYulongglacierandtheenvironmentalresearchstation.ThemeltingdataofHailuo-gouGlacier,BigGongbaGlacierandBaishuiNo.1Glacierin1982and1983comefromabooknamedby“GlacierinHengduanMountains”,whilein1990–1998themeltingdataofHailuogouGlacierisprovidedbyZhangwenjingintheChengduMountainOfficeofChineseAcademyofSciences.Themeteorologicalandhydro-logicaldataofHailuogouGlacierareofferedbytheobservationstationfocusingonthealpineecosystemofMountGongga.Thisstationwasbuiltin1988andaffiliatedwiththeChengduMountainOfficeofChineseAcademyofSciences.ThedataontemperaturevariationinChinaandinNorthernHemisphereusethestudyofWangetal.(1998)forreference.ThedataonmaterialbalanceofHailuogouGlacierfrom1959/1960to1992/1993arefromtheresearchresultofwater-materialbalanceinthebooknamedby“Chineseglacierandenvironment”,andthedataonmaterialbalance 462DataandMethodsduring1993/1994–2003/2004iscalculatedbyauthorwithwaterbalancemethodbasedontheclimatedataandhydrologicaldatain1994–2004fromtheobservationstationfocusingonthealpineecosystemofMountGongga.Thehydrologicaldatain1979–2003ofMujiaqiaohydrologicalstationinYanggongjiangvalleyaretakenfromLijiang’shydrologicalbureau,andtheclimatedataofLijiangBasinarepro-videdbyLijiang’sBureauofMeteorology.2.1.3TheReanalyzedDataTheatmosphericreanalysisdataofNationalCenterofAatmosphericResearch(NCAR)orNationalCentersforEnvironmentalPrediction(NCEP)hastwover-sions:theNCEP/NCARglobalreanalysisproducts(NCEP-R1)andNCEP/DOEsecondsetofreanalysisproducts(NCEP-R2).NCEP-R1producthastwomaincharacteristics.Oneisthecoverperiodofdataislonger,from1948tonow.Theotherisitintegrateinawiderangeoftheobserveddata.NCEP-R2isanupgradeorupdateversionofNCEP-R1.ItchangestheknownsystemerrorofNCEP-R1,andintroducesthelatestphysicalprocess.Thatistosay,itistherecalculationinthecontextofimprovingthesystemofNCEP-R1,therefore,theyhavethesameinputfield,verticalandhorizontalresolution.Theimprovedreanalysissystemcorrecttheproblemsinusingremotesensingtechnologytogetsnowparameters,forexample,theareaandthethicknessofsnow,andimprovetheforecastofwinterprecipitation,groundsurfacetemperatureandsurfacefluxinhighlatitudesregion(Kistleretal.2001;Maetal.2008).ThereanalysisdatasetsofNCEP/NCAR-R1containsthedatafromJanuary1948tonow,anditsspatialresolutionis2.5°×2.5°(Kalnayetal.1996).Itcoverthewholeearth(0–360°E;90°S–90°N);the17isobaricsurfacesinverticaldirectionfromthegroundarerespectively1,000,925,850,700,600,500,600,300,250,200,150,100,70,50,30,20,10hPa.Inaddition,therealsoisthesurfacemeansequencevalues.Thisstudydeterminestheimpactofchangesinatmosphericcir-culationsystemtoclimatechangeofSouthwesternChinabyusingthereanalysisdataofNCEP/NCAR-R1onmonthlymeangeopotentialheight,meridionalandzonalwind,andrelativehumidity.Moreover,thisstudyalsomakeuseofthereanalysisdataonthenetsurfacelong-waveradiation,thenetsurfaceshortwaveradiation,seasurfacetemperature,sealevelpressureandothers.ThereanalysisdataoftheNCEP/NCARonmonthlymeantemperatureandairpressurealsobeusedinthisstudytounderstandthechangeofthesurfacepressuregradientforceandthechangeofwindspeed(Kalnayetal.1996).Andinordertoanalyzethecauseofsunshinetimechanges,thereanalysisdataoftheNCEP/NCARonmeandownwardsolarradiationflux,totalareaofcloudcoverandwatercontentofthecloudandsoforthhasbeenused. 2.2Methods472.2Methods2.2.1TheLinearTrendAreasonablelineardenotestherelationsbetweenclimatevariablesandtime;xidenotesacontainclimatevariables;tidenotescorrespondingtimeofxi.Thenunarylinearregressionequationisdevelopedbetweenxiandti.^xi¼aþbtið2:1ÞInthisformula,aistheregressionconstant;bistheregressioncoefficient.aandbcanbeestimatedbytheleastsquares.Thesymboloftheregressioncoefficientbreferstotheinclinationofclimatevariablesx.Whenb>0,itindicatesthatxisontherisewiththeincreaseoftimet;whenb<0,itindicatesthatxisonthedeclinewiththeincreaseoftimet.Thenumericalsizeofbreflectstherateofriseorfall,thatis,thetendencyofrisingorfalling.Generally,biscalledthetendencyrateofclimate(thatisthechangerange).(a¼xPbtPPnnnxt1xtb¼i¼1PiinðÞi¼P1iðÞi¼1ið2:2Þnn2t21ti¼1inðÞi¼1i1Xn1Xnx¼xi;t¼tið2:3Þnni¼1i¼1Itisnecessarytocalculatethecorrelationcoefficientrinordertoreflecttheclosedegreeofthelinearrelationshipbetweentheclimatevariablesxandtimet.Gen-erally,riscalledtheclimatetrendcoefficient.Pni¼1ðÞxixðÞttrxt¼qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffið2:4ÞPn2Pn2i¼1ðÞxixi¼1ðÞttWhentheabsolutevalueristhegreater,itindicatestherelationbetweenclimatevariablesxandtimetiscloser.Ifwewanttojudgewhethertheclimatechangetrendissignificantornot,significancetextofthecorrelationcoefficientrisstillnecessary.αcanbedeterminedasthelevelofsignificance,iftheabsolutevaluer>rα,itindicatesthatclimatevariablesxchangesignificantlywiththechangeoftimet,oritwasnotsignificant.Thepaperuseρtotext.whenα=0.05,ifr>0.2818,itsuggeststhatthechangetrendisobvious;whenα=0.01,ifr>0.3649,itmeansthatthechangetrendissignificant;Whenα=0.001,ifr>0.4562,itsaysthatthetrendisverysignificant.Inthisstudy,thelinearcorrelationis0.05degreeofconfidence,andthestraightlinepresentsthelineartrend. 482DataandMethods2.2.2MovingMeanMovingmeanisabasicmethodoftrendfitting,whichisequivalenttoalow-passfilterusedtodeterminethechangetrendofmeanofthetimesequence.Forclimatechangesequencexofthesamplesizen,themovingmeansequenceis:1Xk^xi¼xiþj1ð2:5Þki¼1Inthisformula,kisfortheslidinglength,whichisdeterminedaccordingtothespecificmattersandthesizeofthesample.Generally,ktakeanoddnumbersothatthemeancanbeaddedtoeachtimecoordinatesinthetimesequence;j=1,2,…,n−k+1.Theobservedvalueiscalculatedwithmovingmean,andndatacanget(n−k+1)smoothedvalues.Aftersmoothing,thegreatweakeningofcyclewhichisshorterthantheslidinglengthshowsthechangetrend.Basedonpreviousresearches,theclimatechangesequenceinstudyareashastheshortcycleof2,2.5,4,7,9,11,28years.Afterconsideringagain,thelengthoftimesequenceis48years.Theslidinglengthtakeavalueas9,thatmeansthatthechangeofclimatesequenceisaslidingtrendof9years,whichhasbeenmarkedwiththickercurveinthispaper.2.2.3TheCalculationofRegionalTrendInordertoavoidtheeffectofabnormallyhighorlowvaluesfromindividualstationsorinindividualyearstoemperatureandprecipitationsequenceoftheentirearea,firstofall,wemakethemeanvalueofclimatedataofstations,thencalculatethechangesequenceofclimateelementsinthestudyarea.Nextthesequenceofclimateelementsofstationsindifferentperiods,suchasthemonsoonandnon-monsoon,aremadeastheperiodfromDecembertofollowingFebruaryiswinter;theperiodfromMarchtoMayisspring;theperiodfromJulltoAugustissummer;theperiodfromSeptembertoNovemberisautumn;theperiodfromMaytoOctoberismonsoonandtheperiodfromNovembertofollowingAprilisnon-monsoon.Thenwewillcalculatetheannual,seasonal,monsoonandnon-monsoonsequenceofclimateelementsindifferentregions.Thedivisionbetweenmonsoonandnon-monsoonusetheconclusionof“HengduanMountainGlacier”writtenbyLiandSu(1996).Thecalculationresultsofdatainthisstudytakethesignificancelevelof0.05,ifthestatisticalvalueislessthanthesignificancelevel,thetrendisthoughtsignificant.Finally,thespatialdistributiondiagramoftendencyratechangeofclimateelementsisdrawnunderthesituationofArcGIStoanalyzethespatialvariation. 2.2Methods49Theclimatesequenceinstudyareaandthesubregionalareasarecalculatedasthefollowingformula:Xntxr;t¼ðxi;txiÞ=ntð2:6Þi¼1Inthisformula,xr,tistheannualorseasonalmeansoftheclimateparametersofaregion(e.g.,temperature)intyears;xi,tisthevalueofacertainclimateparameterofistaionintyear;xiisthemeanvalueofacertainclimateparameterofistationin1961–2008;ntisthenumberofeligiblestationofacertainclimateparameter.xi,tandxarestandardizedbeforecalculationtoavoidtheinfluenceoftheabnormallyhighvalue.2.2.4TheDefinitionofUrbanStationandRuralStationandtheBasisofClassificationGenerally,themethodtostudytheurbanheatislandeffectistocomparetheobservationsofmeteorologicalstationsinlargecitieswiththatinsurroundingareas(therural),andthedifferencebetweenthemwillbedefinedasthecontributionofcityheatisland(Jonesetal.2008;Renetal.2008).Duetothelimitationofdata,thisstudymainlyanalyzesthedifferenceofchangemagnitudeofeachclimateelementbetweentheruralstationandthecitystation.Alargenumberofclimateresearchesdefinedpopulationasanimportantbasisofclassifyingurbanstationsandruralstations.ThisstudyusetheresearchresultofEasterlingetal.(1997)asreferencetodefinethemeteorologicalstation,ofwhichadministrativeareahasapopulationofmorethan50,000asurbanstation,otherwise,itisruralstation.Basedonthismethod,110stationsinSouthernwesternChinaaredividedinto58ruralstationsand52urbanstations.Inordertodeterminewhethertheregionalterrainwhereobservationstationsarelocatedisinfluentialtotheobservations,wesetaspecificdistanceastheradiustocalculatethealtitudedifferencebetweentheobservationstations(thecenterofacircle)andthesurroundingeightdirectionswiththeuseofGTOPO30digitalelevationmodel(http://eros.usgs.gov).Amongatleastfiveofeightdirections,theelevationdifferencebetweenthemlessthan100misdefinedastheplainstation;lessthan0misdefinedaspeakstations;thatin100–300misdefinedasinter-mountainbasinstation;morethan300mstationisdefinedasthevalleystation.Thenthegeographiccoordinatesofmeteorologicalstationsareinputinthedigitalterrainmaptochecktheabovecalculationresultsandultimatelytodetermineterraintypesofstations. 502DataandMethods2.2.5TheDivisionofSub-regionsInordertomoresystematicallyknowthedifferencesofregionalclimatechange,thisstudymakeafactoranalysistothechangetrendoftheannualmeantemper-ature(standardvalue)of110stationsandseparatetheareaswiththesametem-peraturetrends.Factoranalysisisastatisticalmethodwhichcansortoutseveralvariablesofwhichthecorrelationisquiteclose,andlookeachkindasafactorsoastodistinguishfactorswithdifferentchangingtrend,finallyreachthepurposeofclassification.SouthwesternChinacanbedividesintothreesub-regionsbyusingtheanalysisresultsofchangesfactoroftheannualmeantemperature,thatistodeterminestationswiththeconsistenttemperaturevariationtrends,andcombiningthelatitudelocationandaltitude.Thefirstfactoraccountsfor42%ofthetotalvarianceandisXizangPhateauandHengduanMountains.Itincludes:ShiquanRiver,Bangor,Naqu,Xainza,Shigatse,Lhasa,Zetang,Dingri,Jiangzi,Linzhi,Parry,Suoxian,Bowo,Longzi,Changdu,Dingqing,Shiqu,Ruoergai,sertar,Hongyuan,Dege,Ganzi,Barkam,Daofu,Xiaojin,Batang,Xinlong,Litang,Da-ocheng,Kangding,Muli,Jiulong,Yuexi,Songpan,Yanyuan,Xichang,Deqin,Gongshan,Shangri-la,Weixi,Lijiang,HuapingandDali.Thesecondfactoraccountsforthe33%ofthetotalvarianceandisYunnan-GuizhouPlateau.Itcontains:Huize,Tengchong,Zhaotong,Baoshan,Yuanmou,Chuxiong,Kunming,Zhanyi,Ruili,Jingdong,Yuxi,Luxi,Wenshan,Yiliang,Lincang,Jinghong,Simao,Yuanjiang,Mongla,Jiangcheng,Mengzi,Pingbian,Guangnan,Xianning,Xishui,Panxian,Tongzi,Bijie,Zunyi,Meitan,Sinan,Tongren,Qianxi,Anshun,Guiyang,Kaili,Sanhui,Xingren,Wangmo,Luodian,Dushan,andRongjiang.Thethirdfactoraccountsfor9%andisSichuanBasin.Itincludes:Dujiangyan,Pingwu,Mianyang,Ya-an,Emeishan,Leshan,Zhaojue,Leibo,Yibin,Huili,Guangyuan,Wanyuan,Yanzhong,Bazhong,Daxian,Suining,Gaopingqu,Luzhou,Xuyong,Liangping,Wanxian,Peiling,Shapingba,QiuyangandFengjie.2.2.6TheChangesofAtmosphericCirculationSysteminaLargeScaleOnthebasisofthereanalysisdataonmonthlymeanmeridionalwindfield,monthlyzonalwindfield,relativehumidity,andgeopotentialheightof300and500hPain1961–2008,thisstudyanalyzesthecorrelationbetweenannualmeantemperatureandsealevelpressure(SLP)ofthestudiesareasin1961–2008byusingthesoft-wareofGrads.Basedonthispoint,thisstudysynthesizesthecompositegraphofatmosphericcirculationofisobaricsurfaceof300and500hPainfourseasonsbetween1961–1985and1986–2008.Thevariationcanbegotthroughformerperiodminuslatterone.Moreover,thestudyalsoanalyzestherelationshipbetweenvariationandtemperaturevariationsatthesameperiod.Inthesameway,thecompositegraphofatmosphericcirculationofextrememinimumandmaximum 2.2Methods51temperaturesintheisobaricsurfaceof300and500hPainsummer(June–August)andwinter(December–February)of1961–2008issynthesized,andthecirculationoftwoperiodsispresentedbythatformerminusthelatter.TheextremehightemperatureinsummerinSouthwesternChinaoccurredin1961and2006,whereas,theextremelowtemperatureinsummerhappenedin1965,1968,1974and1976;theextremehightemperatureinwinteroccurredin1987,1999,1987,2003and2007,whiletheextremelowtemperatureinwinterhappenedin1968,1976and1983.Watervaportransportisthemainfactoroftheatmosphericwatercycle,andhasanimportantinfluenceontheregionalclimatechange.Inordertounderstandthechangeofwatervaportransportinthestudyareasanditsimpactonregionalprecipitationvariationunderthebackgroundofclimatechange,thisstudymakesuseoftheNCEP/NCARreanalysisdataonmonthlymeanmeridionalwindfield,zonalwindfieldandrelativehumidityandthegeopotentialheighttocalculatetheintegrallayerofatmosphericvaportransportflux,andanalyzesthevaporfluxchangeanditsimpactonregionalprecipitationvariationunderthebackgroundofclimatewarminginSouthwesternChina.Thespecificcalculationformulaisasfollows:pZ01Q¼ðÞu;vqdpð2:7ÞgptInthisformula,uandvrespectivelyistheeast-westwindsandsouth-northwindofaircolumnperunitareaineachlayeroftheatmosphere;qisthespecifichumidityofaircolumnperunitareaineachlayeroftheatmosphere;P0isthesealevelpressure;Ptispressurewhenitisassumedthatthereisnowatervapourintheatmosphere.Forsimplicitysake,thestudywilltakeP0=1,000hPaandPt=300and500hPa.Accordingtotheprincipleproposedabove,wecalculatethemeanwatervaporfluxof500and300hPaisobaricsurfaceinsummerandwinterof1961–2008andtheannualmeanwatervaporfluxof1986–2008and1961–1985instudyareas.Thevariationispresentedthroughformerminusesthelatter.Inaddition,wealsocalculatethedifferenceofwatervaporfluxofbetweenmoreprecipitationandlessprecipitation,andtheformerminusesthelattertopresentvariation.Insummer,theyearswithmoreprecipitationare1980,1998and1999;theyearswithlessprecipitationare1972,1975,1992and2006.Inwinter,theyearswithmoreprecipitationare1967,1983,1992,1983and2004;theyearswithlessprecipitationare1963,1970and1974.Inaddition,inordertofurtherverifytheinfluenceofthecirculationsystemchangeontheclimateparameterschangeinthestudyarea,thisstudyanalyzestheannualandseasonalchangesofmeridionalandzonalwindinthetwoperiodsof1986–2008and1961–2008,andcalculatethechangeofsolarradiationflux,watercontentincloud,relativehumidityandsooninthedifferentperiods. 522DataandMethods2.2.7TheDefinitionandCalculationofExtremeEventIndexThestandardmethodtodefineandcalculatetheclimateextremeindexinthisstudyis“thedetectionandindexofclimatechange”ofWorldMeteorologicalOrgani-zation(http://cccma.seos.uvic.ca/ETCCDI).Thismethodhasbeenwidelyusedtoresearchextremeweathereventsbyscholarsbothathomeandabroad.Theresearchteamof“thedetectionandindexofclimatechange”finallyidentified27indexesoftheclimateeventswhichconsistof16temperatureindexesand11precipitationindexes.Theseindexesarecalculatedwithdailymaximumtemperature,dailyminimumtemperatureanddailyprecipitation.Themeaningofindexandthebasisofcalculationwillbeshowninfollowingparts.Theaboveindexcanbeclassifiedintofivetypes:(1)relativeindexbasedonpercentagethreshold;(2)absoluteindicatorpresentingmaximumorminimuminaseasonorayear;(3)thresholdindicator;(4)continuousindicator;(5)otherindicators,suchastheannualtotalrainfallofrainyseason,thetemperaturedailyrange(maximumminusesminimum),meanprecipitationintensityinrainydays(precipitationdividesrainfalldays)etc.(Alexanderetal.2006).Nowthemostcommonintheclimateextremechangeresearchontheinterna-tionalisusingapercentilevalueasthethresholdofextremum.Thevaluemorethanthethresholdvalueisconsideredasextremevalue,whichisconsideredtobetheextremeevents.TheclimateextremethresholdisdeterminedbyBonsalnonparametricsolutionsandthecalculationstepsareasfollows:ItisassumedthatameteorologicalelementhasNvalueswhicharearrangedastheascendingorderx1,x2,…,xm,…,xn.Theprobabilityofthatavalueislessthanorequaltoxm:P¼ðÞm0:31=ðÞnþ0:38ð2:8ÞInthisformula,misserialnumberofxm.Thestatisticsofextremetemperaturesistoarrangethetemperaturedataofadayin1961–2008astheascendingorderandtakethe10thandthe90thpercentilevalueasthethresholdofextremetemperature.Whenthetemperatureinadayisgreaterthanthe90thpercentilevalue,itisthoughtthattheextremehightemperatureeventoccursinthatday;whenthelowesttemperatureislessthan10thpercentilevalues,itisthoughtthattheextremelowtemperatureeventhappensinthatday.Thestatisticsoftheextremeprecipitationeventsistoarrangethedailyprecipitationyearbyyearfrom1961to2008astheascendingorderandtakethemeanof48yearsof99thpercentilevalueasthethresholdofextremerainfallevents.Whenrainfallinadayexceedsthethreshold,itisthoughtthattheextremeprecipitationeventsoccursinthatday.WhentheRClimDexsoftwareiscalculatingtheindex,notallindexcalculationbaseonthemonthduetothepracticalapplication.ifthetimeofmissingdataisnotmorethanthreedaysofamonthandnotmorethan15daysofayear,themonthlyandannualextremeindexwillbecalculated;ifthedatainamonthismissing,extremeindexofthisyearswillcalculateincorrectly.Accordingto 2.2Methods53researchneeds,total23climateextremeindexesarechosen,ofwhichcalculationiscompletedwithRclimDex.Thecalculationprincipleoftheselectedindexesisasfollows:1.Thedaysofextremelowtemperatureduringtheday(TX10)inTxijisthedailymaximumtemperatureontheithdayduringj;Tx10isthe10thpercentilethreshold.Therelativeproportionoftheindexisexpressedinthefollowingformula:TxijTnin90,theunitisd.9.Thedaysofextremehightemperatureduringtheday(TX90)Txijisthedailymaximumtemperatureontheithdayduringj;Txin90isthe90thpercentilethreshold.Therelativeproportionoftheindexisexpressedinthefollowingformula:Txij>Txin90,theunitisd. 542DataandMethods10.Thehighvalueofdailymaximumtemperatureinayear(TXx)TXkjisthedailymaximumtemperatureonthekthmonthduringj;themaxi-mumvalueofdailymaximumtemperatureeachmonthiscountedwiththefollowingformula:TXxkj=max(Txkj),theunitis°C.11.Thehighvalueofdailyminimumtemperatureinayear(TNx)TNkjisthedailyminimumtemperatureonthekthmonthduringj;themaximumvalueofdailyminimumtemperatureeachmonthiscountedwiththefollowingformula:TNxkj=max(Tnkj),theunitis°C.12.Thegrowthdaylength(GSL)Tijisthedailymeantemperatureontheithdayduringj;whenthestatisticsfirstlyappear,thereareatleastsixconsecutivedaymeetingthefollowingformula:Tij>5°C;whenthestatisticsfirstlyappearafterJuly1st(NorthernHemisphere),thereareatleastsixconsecutivedaysmeetingthefollowingformulaTij<5°C,theunitisday.13.Thetotalprecipitationintherainday(PRCPTOT)RRijisthedailyprecipitationontheithdayduringj;Iisthenumberofdaysduringj,whichiscountedwiththefollowingformula:XIPRCPTOTj¼RRij;theunitismm:i¼114.Theannualmeanprecipitationintensityinrainydays(SDII)RRwjisthedailyprecipitationinrainydayw(RR≥1mm)duringj;Wisthenumberofrainydaysduringj,whichiscountedwiththefollowingformular:PWw¼1RRwjSDIIj¼;theunitismm=d:W15.Extremeprecipitation(R95)RRwjisthedailyprecipitationinrainydayw(RR≥1mm)duringj;RRwn95isthe95thpercentilethresholdofprecipitationinrainydayduring1961–1990;Wisthenumberofrainydaysduringj,whichiscountedwiththefollowingformular:XWR95pj¼RRwjwhereRRwj[RRwn95theunitismm=d:w¼116.Veryextremeprecipitation(R99)RRwjisthedailyprecipitationinrainydayw(RR≥1mm)duringj;RRwn99isthe99thpercentilethresholdofprecipitationinrainydayduring1961–1990;Wisthenumberofrainydaysduringj,whichiscountedwiththefollowingformular: 2.2Methods55XWR99pj¼RRwjwhereRRwj[RRwn99theunitismm=d:w¼117.Themaximumprecipitationinodddays(RX1day)RRijisthedailyprecipitationontheithdayduringj;themaximumprecipitationinonedayduringjiscountedwiththefollowingformula:Rx1dayj=max(RRij),theunitismm.18.Totalprecipitationinfiveconsecutivedays(R×5day)RRkjistheprecipitationinfiveconsecutivedaysandendinkdayduringj;themaximumprecipitationinfivedayduringjiscountedwiththefollowingformula:Rx5dayj¼maxðRRkjÞ;theunitismm:19.Themaximumconsecutivedroughtdays(CDD)ijRRisthedailyprecipitationontheithdayduringj;themaximumconsecutivedroughtdaysiscountedwiththefollowingformula:RRij<1mm,theunitisd.20.Themaximumconsecutiverainydays(CWD)RRijisthedailyprecipitationontheithdayduringj;themaximumconsecutiverainydaysiscountedwiththefollowingformula:RRij≥1mm,theunitisd.21.Thenumberofdayswhenthedailyprecipitationismorethan10mm(R10mm)RRijisthedailyprecipitationontheithdayduringj;thenumberofdaysiscountedwiththefollowingformula:RRij≥10mm,theunitisd.22.Thenumberofdayswhenthedailyprecipitationismorethan20mm(R20mm)RRijisthedailyprecipitationontheithdayduringj;thenumberofdaysiscountedwiththefollowingformula:RRij≥20mm,theunitisd.23.Thenumberofdayswhenthedailyprecipitationismorethan25mm(R25mm)RRijisthedailyprecipitationontheithdayduringj;nntake25inthisstudy,thenumberofdaysiscountedwiththefollowingformula:RRij≥nnmm,theunitisd.2.2.8TheCalculationofGlacierLengthandMaterialBalanceThedataofterminusfluctuationofglaciersandthechangeinterminuselevationmainlyarebasedonthepreviousresearches(mostlybefore2,000year)andtheobservationofrecentyears(Table2.2).Basedonthispoint,thechangeinlengthofglacieriscountedwiththefollowingformula: 562DataandMethodsL¼L1þDð2:9ÞInthisformula,Listheglacierlength;L1istheglacierlengthincurrentyearusedasareference,thatisthelengthof1982or1983recorded;Disthefluctuatingdistanceofglacierterminus.Iftheglacieradvancespriortothecurrentyear,Disnegativevalue;iftheglacieradvancesafterthecurrentyear,Dispositive.Thefluctuatingspeedofglacierterminusistheratiooffluctuatingdistancetonumberofyears.Theglaciermassbalanceisacombinedactionofresultofclimatefactorslikehydrothermontheglacier,andisoneofthemostsensitiveindicatorsreflectingclimatechange.Itsdynamicchangeisthematerialbasisofthechangeintheglacialscaleandrunoff.Theobservationandestimationofglaciermaterialbalancehavereceivedawideofconcernforalongtime.Inspiteofthehighprecision,thetraditionalmethodgivenprioritytowiththemeasuredstillneedtospendalotofmanpower,materialresourcesandtime,whichlimitstogetobservationsofglaciermassbalanceinalargerscale.Withinthescopeoftheriverbasin,thematerialbalancechangeshavesimilartemporalandspatialvariationcharacteristics.WhenShen(2000)studiedthedistributionofChineseglacialhydrologyandclimate,hefoundtheprecipitationandrunoffdistributionhaveanegativeexponentialrelationwithitsareainthewestplateauland.Theregioncoveredbyglacieristhebiggestdistributionareaofrainfall,runoffandrunoffcoefficient.Startingfromthestatis-ticalmechanicsandthemaximumentropyprinciple,accordingtothecharacteristicsofprecipitationandrunoffdistribution,asetofequationsusedtocalculatetheglaciersmeanmaterialbalancewithhydrologicalandmeteorologicalobservationdatahavebeendeduced.Onthebasisoftheseformulas,wewillbeabletoresumetheyear-to-yearchangingsequenceofthemeanmaterialbalancewiththeappli-cationofunoffandprecipitationdatarecordedinhydrologicstations,whichhasarealisticmeaningtosystematicallyresearchthematerialbalanceofallthemoun-tainsandbasinsandtorecovertheunderstandthehistoryofglaciermassbalanceandtheinfluenceofglacierchangeonrunoff.ThisstudycalculatesmaterialbalanceofHaiLuoGouglacierduring1993/1994–2003/2004withwaterbalancemethod,anditsprincipleisasfollows:Bn¼ðÞPER=Kð2:10ÞInthisformula,Bnisglaciermassbalance,Pisthebasinrainfall,Ristherunoff,Eisevaporation,Kisglaciercoverageinthebasin.2.2.9TheCalculationofWaterOutputinSnowandIceatHighAltitudesMountGongga(29°20′−30°20′N,101°30′–102°15′E)andMountYulong(27°10′–27°40′N,100°9′–100°20′E)arethetypicalMarineglacierareas.HaiLuo-GouriverbasinislocatedintheeastslopeofGonggamountainandfinallyfallsinto 2.2Methods572theDaduRiver.Thereareeightglacierswithatotalareaof29.66km(Pu1994)in2thisbasin,andthetotalareaofHaiLuoGouriverbasinis78.07km.Thewholeriverbasinconsistsofmountains,ofwhichminimumaltitudeis2,920m.Theareasbelow3,800marecoveredbyvegetation,whiletheareasabove3,800marecoveredbyiceandsnow.Themainwaterinputinthisriverbasinisfrompre-cipitationandiceandsnowmeltingwater.GonggaMountainstationinChengdulandofficebegantoobservethehydrologicalconditionin1994,whichislocatedintheHaiLuoGouglacierterminusof1km.Yanggongjiangbasinislocatedatthe2southerntipofYulongsnowmountain,withinwhichtheglacierareais2.44km(Pu1994).ThemeltingwaterfeedsintotheLijiangBasionandfinallyfallsintoYanggongjiang.Lijiang-YulongSnowMountainregionismainlycoveredbylimestones,andtherockdissolvephysiognomyisrelativelydeveloped.SotheprecipitationandthemeltingwaterofYanggongjiangbasincanmoreeasilyinfil-trateintoundergroundandformundergroundwater,thenpouroutsurfaceinlowerplaceofLijiangbasinformingmanymouthstorechargethesurfacerunoff.In1979,hydrographicofficeofLijiangcountysetupahydrometricstationinmainlycon-2trollingtheYangjiangriverbasin.Theareascontrolledis436.8kmandmainlyiscomposedofYulongsnowmountainlandandLijiangBasin.Amongtheseareas,2snowandice-snowregionathighaltitudewhichismorethan4,000mis13.8km,2andtheotherareais423.0km.Ascalculatingthewaterbalanceofrivebasin,wejustneedtotakethebalanceofnonice-snowregionatlowaltitudeintoconsideration,likeLijiangBasin,becausetherearenottheobservationdataofprecipitationandglaciermeltingwaterrunoffathighaltitude.Atthesametime,weapproximatelythinkice-snowregionathighaltitudeasoneofinputitemofthatregionatlowaltitude,thatisPGlacier,withoutthedistinctionbetweentheliquidprecipitationandglaciermeltingwater.Inaddition,theprecipitationisanotherinputitem,thatisP.Andtheoutputitemsincludewatershedrunoff(D)andtheactualevaporation(E).Therefore,theequationofwaterbalanceinthelowaltitudeareacanbepresentedasEq.(2.11):PGlacierþP¼DþEð2:11ÞAmongthem,theactualevaporationEcanbecalculatedwithpotentialevaporationE0.AccordingtothecalculationofmonthlyevaporationE0intworiverbasinswithBaney-Criddlemodel,Yangetal.(1994)showedthattheactualevaporationcal-culatedwiththisformulacanpresenttheactualevaporationoftheentirebasin.ReferencesAguilar,E.,etal.(2005).ChangesinprecipitationandtemperatureextremesinCentralAmericaandnorthernSouthAmerica,1961–2003.JournalGeophysicalResearch,110(D23),107.Alexander,L.V.,etal.(2006).Globalobservedchangesindailyclimateextremesoftemperatureandprecipitation.JournalGeophysicalResearch,111(D05),109. 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Chapter3SpatialandTemporalVariationofTemperatureandPrecipitationinSouthwesternChina3.1TemporalVariationofTemperatureandPrecipitation3.1.1MeanTemperatureandPrecipitationThemeantemperatureinSouthwesternChinain1961–2008is12.7°C,andthemeantemperatureinspring,summer,autumn,winter,monsoonperiodandnonmonsoonperiodare13.3,19.9,13.1,4.5,7.5and17.9°C,respectively.Theannualandseasonalmaximumtemperatureare23.8,25.6,28.3,23.7,17.6,20.3and27.3°C,respectively,whichappearinYuanjiangstation,YunnanProvinceatlowlatitudeandaltitude.Theaccordingminimumtemperatureare−1.3,−1,7.5,−1.1,−11.5,−8.1and5.2°C,respectively,whichmainlyoccurinShiqu,Naqu,Palietc.athighaltitude.Theannualmeanprecipitationin1961–2008is965mm,andthemeanprecipitationinspring,summer,autumn,winter,monsoonperiodandnonmonsoonperiodare188,501.4,218.9,41.8,157and796.7mm,respectively.Theprecipitationinspring,autumnandmonsoonperiodaccountfor82.6%ofannualmeanprecipitation.Theannualandseasonalmaximumprecipitationare2,251.7,577.5,1,273.6,501.5,224.2,699.3and1,929.7mm,respectively,whichhappenintheJiangchengstation,YunnanProvince.Theaccordingminimumprecipitationare285.2,9.17,95.5,22.2,0.4,3.0and63.14mm,respectively,whichoccurinDingriandTsetangstation,XizangAutonomousRegion.AsshowninFig.3.1,thespatialdistributionofthemeanannualandseasonaltemperaturedeclinesgraduallyfromsouthwesttonortheast.ThemaximumtemperatureisdistributedintheYunguiPlateauandSichuanBasin,whiletheminimumtemperatureisdistributedintheXizangPlateauandHengduanmountain.Thespatialdistributionofthemeanannualandseasonalprecipitationissametothetemperature(seeFig.3.2),andreflectsthesignificantinfluenceoftopographyandelevation.ThemeanannualandseasonaltemperatureofXizangPlateauandHengduanmountainin1961–2008are7.0,7.5,14.5,7.4,−1.2,1.7and12.4°C,respectively,andthemeanannualandseasonalprecipitationare674,113.6,372.8,©Springer-VerlagBerlinHeidelberg201561Z.Li,StudyonClimateChangeinSouthwesternChina,SpringerTheses,DOI10.1007/978-3-662-44742-0_3 623SpatialandTemporalVariationofTemperature…Fig.3.1Spatialdistributionofthemeanannualandseasonaltemperatureduring1961–2008inSouthwesternChina,aannual,bspring,csummer,dautumn,ewinter,fwintermonsoonperiod,gsummermonsoonperiod 3.1TemporalVariationofTemperatureandPrecipitation63Fig.3.2Spatialdistributionofthemeanannualandseasonalprecipitationduring1961–2008inSouthwesternChina,aannual,bspring,csummer,dautumn,ewinter,fwintermonsoonperiod,gsummermonsoonperiod 643SpatialandTemporalVariationofTemperature…148.8,19.7,84.1and574.3mm,respectively.Accordingly,themeantemperaturesinSichuanBasinare16.0,16.2,24.7,16.5,6.7,10and22.0°C,respectively,andthemeanprecipitationare1,148.3,233.7,572.0,276.7,51.5,209.0and937.0mm,respectively.Thedifferencebetweentemperatureandprecipitationofsub-regionsconfirmsagaintheinfluenceoftopographyandelevationonthedistributionofregionaltemperatureandprecipitation.3.1.2TheAnnualChangeofTemperatureInthepast50years,thetemperatureinSouthwestChinaincreasegradually,andthemagnitudeofwarmingis0.33°C/10a.Themagnitudeofwarmingissmallerbeforethemidof1980s,whereasthemagnitudeisrelativelybiggerafterthemidof1980s,whichsuggeststhewarmingisacceleratinggradually(Fig.3.3).Thesignificantwarmingtrendcanalsobeshownintheseasonvariation.Themagnitudesoftemperaturevariationinspring,summer,autumnandwinterare0.18,0.19,0.26and0.24°C/10a.Since1961,themeantemperatureinwintercontinuedtorise.Thesummermeanshowedatrendoffluctuatingdownwardandkeptaslowrise,butthemagnitudeofrisingincreased;thespringmeanincreasein1960sfollowedbyanacceleratedriseinthemidof1989s,thenappearaslowdeclinefrom1970stothemidof1980s(seeFig.3.3).WhatthedifferencefromotherregionsisthatthesharprisingoftemperatureinSouthwestChinamainlyoccursinautumn,butthebigmagnitudeofwarminginautumnandwinterissimilartothatofQinglianmountainsandXinjiangAutonomousRegion(Fig.3.1).Intermsofthemeanannualtemperature,themagnitudeofchanginginXizangPlateau–Hengduanmountains,SichuanBasinsandYunnan-GuizhouPlateauare0.36,continuedtorisein1961–2008;thetemperatureinYunnan-GuizhouPlateaukeptatableriseexceptforthefluctuatingdowntrendin1960s;thetemperatureinSichuanBasinsshowedawavelikedecreasechangebefore1985followedbyasignificantrise(Fig.3.3).ThemagnitudeoftemperaturevariationinspringinXizangPlateau–Hengduanmountains,SichuanBasinsandYunnan-GuizhouPla-teauare0.23,0.13and0.13°C/10a.TheSichuanBasinsfailedtobeestimatedthesignificantlevel.ThetemperatureinSichuanBasinsandYunnan-GuizhouPlateaushowatrendoffluctuatingdownwardfromtheendof1980stobeginningof1990s.Amongthem,themagnitudeofdecliningoflatterisbigger.Thereafter,thetem-peratureinthesetwoareaskeepastablerise.WhilethetemperaturekeepasharpriseinXizangPlateau–Hengduanmountains(Fig.3.3).ThesummertemperatureinXizangPlateau–Hengduanmountains,SichuanBasinsandYunnan-GuizhouPla-teauincreaseattherateof0.29,0.22and0.04°C/10a.TheSichuanBasinsfailedtobeestimatedthesignificantlevel.ThetemperatureinXizangPlateau–Hengduanmountainscontinuedtorisein1961–2008;thetemperatureinYunnan-GuizhouPlateaushowedawavelikedecreasechangein1960s,andrisedfrom1970stothemidof1980s,thenwasonaslowdeclinefollowedbyarisefrom21stcentury.InSichuanBasin,themidof1980sisawatershed.Beforethistimethetemperature 3.1TemporalVariationofTemperatureandPrecipitation65Fig.3.3Inter-annualvariationoftemperatureduring1961–2008 663SpatialandTemporalVariationofTemperature…showedasteppeddecrease,whereasafterthistimeitshowedasteppedincrease(Fig.3.3).Themagnitudeoftemperaturevariationinautumninthesethreeregionsare0.25,0.23and0.26°C/10a,respectively.WhatthedifferencefromotherseasonsisthatthemagnitudeofwarminginSichuanBasinisbiggestfollowedbyXizangPlateau–Hengduanmountains.ThetemperatureinSichuanBasinsandYunnan-GuizhouPlateaudecreasedslowlybeforethemidof1970s,thenwasonacon-tinuousrise(Fig.3.3).Themagnitudeoftemperaturevariationinwinterinthesethreeregionsare0.29,0.22and0.19°C/10a,respectively.Alltheyshowedariseduringthestudy(Fig.3.3).Exceptforinautumn,themagnitudeoftemperaturevariationinXizangPlateau–HengduanmountainsisbiggestandmorethanthatofwholeSouthwesternChina.Thedifferenceofmagnitudeoftemperaturevariationinthesub-regionsreflectstheinfluenceoftopography.ThemagnitudeofwarminginXizangPlateau–Hengduanmountainsislargerinwinterandsummer;themagni-tudeofwarminginSichuanBasinsandYunnan-GuizhouPlateauislargerinautumnandwinter;whilethetemperatureofSichuanBasinisnonsignificantincreasetrendinspringandsummer.ComparedwithotherregionsinChina,thewarmingmagnitudeofmeanannualtemperatureofSouthwesternChinaissmallerthanthatofNortheasternChinaandXinjiangAutonomousregions,butlargerthanthatofNorthwesternChina,QilianMountainandHimalayaMountains.Inaddition,themagnitudeofwarminginautumnismuchlargerthanHengduanMountains,NorthwesternChinaandXinjiangAutonomousregions(Fig.3.1).3.1.3TheAnnualPrecipitationVariationTheprecipitationofSouthwesternChinashowedanon-statisticallysignificantdecreasein1961–2008.Themagnitudeofchangingwas−0.006mm/10aandkeptstablein1961–1980,thenhadaslowdecline.Butitwasrisingsignificantlyinthewhole1980s,whileshowedawavelikedeclinetrendafternewcentury(Fig.3.4).Themagnitudeofprecipitationvariationinfourseasonswere0.061,0.023,−0.077and0.093mm/10a,respectivelyinstudyareas.Itshowedastatisticallysignificantdecreaseasawhole,althoughtherewasaslowincreasetrendinthemidof1970s;theprecipitationinsummerhadafluctuatingchangefromincreasetodecreaseasacycleofabout10years;theprecipitationinwintershowedaslowincreaseinastatisticalsignificance;whiletheprecipitationhadanobviousfluctuationbefore1980sfollowedbyarisingtrend(Fig.3.4).ThemagnitudeofannualprecipitationvariationinXizangPlateau–HengduanMountains,SichuanBasinsandYunnan-GuizhouPlateauwere0.085,−0.049and−0.088mm/10a.Amongthem,onlytheprecipitationofXizangPlateau–HengduanMountainswasslowlyincreaseinfluctuation.TheprecipitationofYunnan-Guiz-houPlateaufluctuatedtodelincebefore1990sandhadaobviousrisein1990s,butitfluctuatedtodelinceagainafter2000.TheprecipitationofSichuanBasinkeptthetrendoffluctuatingdeclineallthetimeinrecent50years(Fig.3.4).Themagnitude 3.1TemporalVariationofTemperatureandPrecipitation67Fig.3.4Inter-annualvariationofprecipitationduring1961–2008 683SpatialandTemporalVariationofTemperature…ofspringprecipitationvariationinthesethreeregionswere0.187,0.024and−0.039mm/10a.TheprecipitationofXizangPlateau–HengduanMountainshadasignificantincrease,whereastheprecipitationofSichuanBasinhadaslowdecrease.TheprecipitationofYunnan-GuizhouPlateauwasonarisein1961–1975,butitdelincedin1975–1990.Thereafteritrisedagain(Fig.3.4).Themagnitudeofsummerprecipitationvariationinthesethreeregionswere−0.006,−0.02and0.039mm/10a.TheprecipitationofXizangPlateau–HengduanMountainsslowlydeclinedin1970s,thenkeptastabletrenduptothemidof1990s.In1995–2005itappearedarise,butitdeclinedafter2005.TheprecipitationofYunnan-GuizhouPlateaufellinfluctuationbefore1990sandroseinthewhole1990s,thenitappearedasignificantdecline.Beforethemidof1980stheprecip-itationofSichuanBasinshowedawavelikeincrease,thenitslowlydecreased.Ingeneral,itshowedarisingtrend(Fig.3.4).TheautumnprecipitationofXizangPlateau–HengduanMountainsshowedatrendoffluctuatingincreasebefore1990s,thereafteritfluctuatedtodecrease.Themagnitudeofchangingis0.061mm/10a.TheprecipitationofYunnan-GuizhouPlateaudecreasedattherateof−0.101mm/10ain1961–2008.TheautumnprecipitationofSichuanBasindeclinedsignifi-cantlyattherateof−0.2mm/10ainnearly50years(Fig.3.4).ThewinterprecipitationofXizangPlateau–HengduanMountainshadaobviousriseinfluc-tuation,ofwhichmagnitudeis0.11mm/10a;thewinterprecipitationofYunnan-GuizhouPlateauslowlyincreasedattherateof0.058mm/10a;thatofSichuanBasinhadawavelikedecreasebefore1980s,anditbegantoincreaseupto1990s,butitdeclinedinfluctuationagain(Fig.3.4).Asawhole,comparedwiththetemperaturevariation,themagnitudeofprecip-itationvariationissmaller,buttheannualfluctuationreflectsthecomplexityandthedifferenceinregions.Theprecipitationinwinterandspringsignificantlyincrease,whileitdecreasessharplyinautumn.TheprecipitationofXizangPlateau–HengduanMountainsinwinterandspringmuchmorethanthatofSouthwesternChina,andtheannualandautumnprecipitationofSichuanBasinsandYunnan-GuizhouPlateauaremorethanthatofSouthwesternChinaaswell.Comparedwithotherregions,themagnitudeofprecipitationvariationinSouthwesternChinaissmallestin1961–2008andgenerallyisinastablestate(Table3.1).3.1.4Inter-annualVariationofTemperatureandPrecipitationinMonsoonPeriodandNonMonsoonPeriodTheannualmeantemperatureofSouthwesternChinainmonsoonperiodandnonmonsoonperiodincreasedattherateof0.2and0.28°C/10afrom1961to2008,andthemagnitudeofrisingobviouslyenlargedafterthemidof1980s(Fig.3.5).In1961–1961,theprecipitationinmonsoonperiodbasicallykeepinastablestateandhasbeeninaslowfluctuation.Thereafter,thefluctuatingrangeenlargeobviously. 3.1TemporalVariationofTemperatureandPrecipitation69Table3.1Comparisonoftemperature(°C/a)andprecipitation(mm/a)changeinSouthwesternChinawithotherregionsofChinaRegions/periodAnnualSpringSummerAutumnWinterDatatemperaturetemperaturetemperaturetemperaturetemperaturesourcesCentralTibet/0.240.160.26Bian1961–2000andDu(2006a)Qilian/0.300.180.260.380.50Jiaetal.1960–2005(2008)Himalaya/0.23Yangetal.1971–2004(2006)Xinjiang/0.330.740.941.942.07Liuetal.1960–2005(2009)Gansu/0.21Wuetal.1957–2006(2008)Northeastern0.360.40.130.20.6DongandChina/Wu1953–2001(2008)Northwestern0.26Yaoetal.China/(2009)1951–2004Yunnan/0.15Chengand1960–2007Xie(2008)SB/1951–2000−0.03Chenetal.(2008)Hengduan0.150.590.150.170.35Lietal.mountains/(2010d)1960–2008Southwestern0.330.180.190.20.24ThisstudyChina/1961–2008Regions/periodAnnualSpringSummerAutumnWinterDataprecipitationprecipitationprecipitationprecipitationprecipitationsourcesCentralTibet/19.9Bianand1961–2000Du(2006a)Qilian/11.83.23.630.6670.967Jiaetal.1960–2005(2008)Xinjiang/8.54.5417.146.637.29Liuetal.1960–2005(2009a,b)Gansu/−3.17Wuetal.1957–2006(2008)Northwestern−21.44Yaoetal.China/(2009)1951–2004SB/1951–2000−22.56Chenetal.(2008)Hengduan9.098.62−1.51.531.47Lietal.mountains/(2010d)1960–2008Southwestern−0.0060.0610.023−0.0770.093ThisstudyChina/1961–2008 703SpatialandTemporalVariationofTemperature…Fig.3.5Inter-annualvariationoftemperatureandprecipitationinsummermonsoonperiodandwintermonsoonperiodduring1961–2008 3.1TemporalVariationofTemperatureandPrecipitation71Theprecipitationinnonmonsoonperiodslowlyincreasesattherateof0.044mm/10a.Theinter-annualvariationtransfersfromtheriseof1961–1975todeclinationof1976–1985,thenslowlygoesupafterthemidof1980s(Fig.3.5).ThemagnitudeoftemperaturevariationinmonsoonperiodinXizangPlateau–HengduanMoun-tains,SichuanBasinsandYunnan-GuizhouPlateauare0.26,0.19and0.15°C/10a.Alltheyshowastatisticallysignificantwarming.ThetemperatureofSichuanBasinslowlydeclinedbeforethemidof1980s,thenobviouslyrose.ThetemperatureofYunnan-GuizhouPlateauchangedastheshapeofW.Inotherwords,itfellin1960sandrosein1970–1985,thenslowlydeclinedin1985–1995.Thereafter,itshowedasignificanttrendofrising(Fig.3.5).Themagnitudeoftemperaturevariationinnonmonsoonperiodinthesethreesub-regionsinturnare0.32,0.25,and0.22°C/10a,andalltheyhaveundergonesignificancetest(Fig.3.5).ThetemperatureofSichuanBasininmonsoonperiodhadaslowdeclinebeforethemidof1980s,however,thetemperatureofYunnan-GuizhouPlateauandXizangPlateau–HengduanMountainskeptasignificantrisingtrendallthetime.TheprecipitationofXizangPlateau–-HengduanMountainsinmonsoonperiodslowlyincreaseinfluctuationattherateof0.057mm/10a,whichshowedawavelikedeclinein1960s,thenhadawavelikerise.WhiletheprecipitationofYunnan-GuizhouPlateauhadaslowdecreaseinfluctuationattherateof−0.029mm/10a.Ithadbeeninadroppingtrendallthetimeexceptforthe1990s.Innearly50years,theprecipitationofSichuanBasinhadasustaineddownwardtrendbyrateof−0.069mm/10a(Fig.3.5).TheprecipitationofSichuanBasininnonmonsoonperiodshowedaslightdropbyrateof−0.04mm/10a,anditsinter-annualvariationpresentedachangeastheshapeofVwiththe1980sbeingthedividedpoint(Fig.3.5).TheprecipitationofYunnan-GuizhouPlateauinnonmonsoonperiodalsoslowlydeclinedattherateof−0.043mm/10a,anditsinner-annualvariationhadaobviousfluctuation.Amongthesethreesub-regions,thereonlyprecipitationofXizangPlateau–HengduanMountainsinnonmonsoonperiodsignificantlyincreaseattherateof0.184mm/10a,whichindicatestherisingtrendofprecipitationathighaltitude(Fig.3.5).3.1.5TheTemperatureandPrecipitationVariationReflectedbyIceCoresandTreeRingsTheicecoreaccumulationofDasuopulocatedinthecentralpartofHimalayasMountaindeclinedsignificantlysince1930,whichmayreflectthereductionofprecipitation(Duanetal.2002).ThestudyontheicecoreofEverestregionsuggestedtheaccumulationsharplydroppedinthe1950sand1960s,thenkeptaslowdeclination.ThisphenomenonalsoreflectsthatoneoftheremarkablefeatureofclimatechangeinthecentralpartofHimalayasMountainisprecipitationdecrease.However,theanalysisoftheicecoreisotopeinthisregionconfirmedthesignificantwarmingtrend.Basedonthispoint,Renetal.(2003)consideredthattemperatureincreaseandtemperaturedecreaseaswellasthewarmanddryclimate 723SpatialandTemporalVariationofTemperature…causedbythesharpincreaseofsummertemperaturearethemainreasonofglacierchangeinthisregion.Theseconclusioncanbeconfirmedinthisstudy.Theanalysisfoundthattheannual,autumnandmonsoonprecipitationofthecentralpartofHimalayasMountainhadaobviousdecreaseinrecent50years.ThestudyofHouandZhang(2003)ontheicecoreaccumulationofEastRongbukandfarEastRongbukindicatedthatintwoperiodsof1954–1963and1964–1997,theaverageaccumulationoficecoreineachperiodwere581.7and321.2mm,267.5and150.3mm,whichshowedasharpdropoverthepast50years.ThestudyofZhangetal.(2004)ontheicecorerecordsofEastRongbukfoundthattheprecipitationvariationathighaltitudehadamuchsensitivitythanatlowaltitude.ThestudyofKangandQin(2000)ontheicecorerecordsoffarEastRongbukinthenorthslopeofEverestconfirmedthatthewarmingtrendofthisregionand1974–1986wasaremarkedwarmingperiod.TheresearchofZhangetal.(2007a,b)onGeladandongicecoredeterminedthattheaccumulationdramaticallyraisedsince1960,andtheannualmeanaccumulationintheperiodfromtheendof1960stothebeginningof1990wasabout1.5timesmorethanbefore1960s.Buttheaccumulationstartedtofallcontinuouslyafterentering1990s.Thischangeisconsistenttheannualprecipitationvariationofnearbystations,suchasNaqu,LhasaandBangor.Inaddition,thefurtherstudyoftheicecoresalsoconfirmedthesummertemperaturesignificantlyroseandannualtemperatureacceleratedafter1970s.Yaoetal.(2006)madeasummaryabouttheicecorerecordsofPiruogangriandthoughtthatthetemperatureinQinghai–XizangPlateaushowedasignificantwarmingoverthepast100years.ThroughthecomprehensiveanalysisoficecoreaccumulationinQinghai–XizangPlateau,Houetal.(2002)pointedoutthattheicecoreaccumulationofDongkemadilocatedinnorth-centralplateauhadbeenonariseingeneralsince1950.Whileseveralicecoreaccumulationinthesouthernplateaushowedaobviousdownwardtrend.Thefurtheranalysisindicatedthatmaybetherearetworeasonsresultedinaccumulationreduction:lessrainfallanddramaticalmeltingcausedbysharpriseoftemperature.Moreover,theresearchonthesnowandiceprofileenvironmentrecordsofBaishuiNo.1confirmedthatthemainreasonofaccumulationreductionisdramaticalmeltingcausedbysharpriseoftemperature.Accordingtotheanalysisofwidthdataoftreering,Songetal.(2007)foundthatmeanminimumtemperatureofJouzhaigouareainwinterhalfyearhadbeeninthehigh-valuedurationandsignificantlyrosefrom1984tonow.Zhangetal.(2010)foundthattreeringrecordscouldpointedouttheautumnandwintermeanmini-mumtemperatureinChangdu,Xizangrosesignificantlyinthe1970sand1980s,andthewinterminimumtemperaturegraduallyrosesincetheendof1960s.ThestudyofFanetal.(2008)thoughtitisasignificantwarmperiodsince1990inthecentralpartofHengduanMountains.ShaoandFan(1999)pointedoutthatthewinterminimumtemperatureofwesternSichuanheatupsignificantlysincethe1960sbymeansofthewidthdataoftreering.Duanetal.(2010)reconstructedthetemperaturevariationfromAugusttoSeptemberinthepast171yearsin 3.1TemporalVariationofTemperatureandPrecipitation73Gonggamountainareasbymeansoftreeringchronology(RC).TheresultsshowedthattheabnormalhightemperatureyearsofmeantemperatureofAugustandSeptemberhave22years,andtheabnormallowtemperatureyearshave23years.Amongthem,therearefourobviouslowtemperatureperiods,including1837–1842,1884–1891,1899–1905and1984–1989;andthreeobvioushightemperatureperiods,including1966–1973,1916–1924and1876–1881.TheaboverecordsaremainlyfromthehighaltitudeareasofHimalayas,Mount.Tunggula,NyenchenTanglhaandHengduanMountain,wherethereareafewmeteorologicalobservationstations(Fig.3.6).Theseresearchresultsshowtwopoints.Intheonehand,theyreflectthesignificantwarmingofhighaltitudeareasanddemonstratethesignificantelevationeffectoftemperature;intheotherhand,theyalsoreflecttheuncertaintyofprecipitationvariationinhighaltitudearea.Theicecoreaccumulationshowsanobviousdecreasetrend,especiallyafterthemidof1980s,whichislikelytobecausedbyintensifiedmeltingandincreasingliquidprecipitationunderthebackgroundofwarming.Therefore,thewarmanddrycli-mateinsomeregionsofXizhangPlateaucanbeconfirmedbythecombinationofstationsrecordsandicecoresrecords,forexample,thecentralpartofHimalayas.Fig.3.6Spatialdistributionof7icecoresand4treeringsreflectedtemperatureandprecipitationvariationinstudyareafromthepreviousresearches 743SpatialandTemporalVariationofTemperature…3.2SpatialVariationofTemperatureandPrecipitation3.2.1TheSpatialDistributionofTemperatureVariationExceptforanumberofstationsinSichuanBasin,thesoutheasternregionofHengduanMountainandGuizhouPlateau,thereabout92%ofthestationsinSouthwesternChinashowedawarmingtrendfrom1961to2008;thewarmingtrendof77%hadsucceededinthesignificancetext.ThemagnitudeoftemperaturevariationinXizangPlateau–HengduanMountainandYunnanPlateauaremuchlarger,andthestationswithasignificantwarmingarealsomainlydistributedintheseregions.WhilethestationswithnonsignificantwarmingmainlyarelocatedinSichuanBasin(Fig.3.7).Thespringtemperatureofabout85%ofthestationsobviouslyincreased,butonly45%ofthestationsshowedthesignificantincrease.ThesestationsareprincipallydistributedinXizangPlateau,thenorthandsouthofHengduanMountainandthewestofYunnanPlateau.ThespringtemperatureofpartialstationsinsoutheastofHengduanMountainandtheeastofYunnanPlateaudeclinedsignificantly,theareaswithnonsignificantwarmingarechieflyinSichuanBasinandGuizhouPlateau(Fig.3.7).Themagnitudeofsummertemperaturevariationofabout82%ofthestationswaspositive.About54%ofthestationsshowedasignificantwarmingtrend,whichmainlyweredistributedinXizangPlateau–HengduanMountainandYunnanPlateau.However,thespringtempera-turesofalargenumberofstationslocatedintheSichuanBasindecreased,andthestationswithnonsignificantwarmingarechieflyintheedgeofSichuanBasinandGuizhouPlateau(Fig.3.7).ExceptforanumberofstationsinYunnan–GuizhouPlateauwithadeclinedtemperature,theautumntemperatureofabout92%ofthestationsinSouthwesternChinashowedawarmingtrend.Amongthem,thewarmingtrendof77%hadsucceededinthesignificancetext.Comparedwiththespringandsummertemperature,theautumntemperatureintheedgeofSichuanBasinandthenorthernregionofGuizhouPlateauwasontherise.Whereas,anumberofstationslocatedinthenorthernregionofHengduanMountainandtheeastofYunnanPlateaupresentanonsignificantwarmingtrend(Fig.3.7).Thewintertemperatureofabout95%ofthestationsinthestudyareashowedawarmingtrend,thenumberofwhichaccountedfor59%oftotalstations.ThesestationsaremainlydistributedinXizangPlateau–HengduanMountainandYunnanPlateau.MorestationsinSichuanBasinandGuizhouPlateauhadanonsignificantwarmingtrend(Fig.3.7).Ingeneral,themagnitudeoftemperaturevariationgraduallyreducedfromwesttoeast.ThestationswithsignificantwarmingandlargemagnitudeofwarmingwereprimarilydistributedinXizangPlateau–-HengduanMountainandYunnanPlateau,whilethestationswithnonsignificantwarmingtrendwerelocatedinSichuanBasinandGuizhouPlateau.Thisdistri-butioncharacteristicconfirmedthewidermarginofwarminghappenedinhighaltitudeareas.Inaddition,themoststationssignificantlywarmedinautumnandwinter,whichreflectedthespecialseasonalstructureofthewarmingonceagain. 3.2SpatialVariationofTemperatureandPrecipitation75Fig.3.7Spatialdistributionoftemperaturevariationduring1961–2008.ReprintedbypermissionfromIOPPublishing:Ref.(Lietal.2011).Copyright(1993),aannualtemperature,bspringtemperature,csummertemperature,dautumntemperature,ewintertemperature3.2.2TheSpatialDistributionofPrecipitationVariationTheannualprecipitationofabout53%ofthestationsinsouthwestChinashowanincreasemomentum,butonlyabout5%ofthestationsincreasesignificantlyandmainlyarelocatedinXizangPlateau.Thestationswithanincreasetrendalsoaremainlydistributedinhighaltitudearea.Amongthem,somestationsinthecentralsectionoftheXizangPlateau–HengduanMountainhavealargermagnitude,whilethestationswithreducingprecipitationaremainlylocatedineasternYunnanPlateau, 763SpatialandTemporalVariationofTemperature…GuizhouPlateauandSichuanBasin.Thestations,ofwhichprecipitationreducebyawidemarginaremainlydistributedinregionsaroundtheSichuanBasin(Fig.3.8).Thespringprecipitationofabout70%ofthestationsshowanincreasemomentum,andthestationswithawidermarginarelocatedinHengduanMountainandYunnanPlateau.ThestationsinthesouthofXizangPlateau–HengduanMountainwhichaccountforabout20%oftotalstationshaveasignificantincreaseinprecipitation.AlmostallstationsinGuizhouPlateauandSichuanBasinshowadowntrend,andthereducingmagnitudeofGuizhouPlateauiswideramongthem(Fig.3.8).Only50%Fig.3.8Spatialdistributionofprecipitationvariationduring1961–2008.ReprintedbypermissionfromIOPPublishing:Ref.(Lietal.2011).Copyright(1993),aannualpercipitation,bspringpercipitation,csummerpercipitation,dautumnpercipitaiton,ewinterpercipitation 3.2SpatialVariationofTemperatureandPrecipitation77ofstationsperformanceincreasetrendinsummerprecipitation,exceptfortheXizangPlateau–HengduanMountain.WhatthebiggestdifferencewithspringprecipitationisthatthesummerprecipitationofallstationsintheeasternSichuanBasinandGuizhouPlateaushowanincreasingtrend.However,theprecipitationofstationsinwesternSichuanBasin,thesouthwestandnorthofHengduanMountain,theeastandsouthwestofXizangPlateauandthewholeYunnanPlateau.Amongthem,anumberofstationsinthewestofYunnanPlateauandthewestofSichuanBasinpresentanoppositetrendwithspringprecipitation,thatisthesummerprecipitationhaveawidermagnitudeofvariation(Fig.3.8).Comparedwithotherseasons,themostremarkablecharacterofautumnisthattheareaofprecipitationreductionsignificantlyincrease.Thesestationsaccountforabout65%ofthetotalstations.Amongthem,thereareabout12%ofstationsdistributedinSichuanBasinandGuizhouPlateau.Inaddition,alargenumberofstationsinnorthernandsouthcentralHengduanMountain,theeastandsouthwestofYunnanPlateauandthethreestationsinthecentralpartofHimalayashowadownwardtrend,amongwhichthemagnitudeofprecipitationreductioniswidest(Fig.3.8).TheregionofprecipitationincreaseinSouthwesternChinaiswidestinwinter.Thereareabout77%ofthestationswiththerisingtrend,among11%ofthestationsincreasesignificantly,whicharelocatedinthenorthpartofXizangPlateau–HengduanMountain.AlmostthewinterprecipitationofallstationsinSichuanBasinandGuizhouPlateauincreasesimilartothespatialdistributionofsummerprecipitation.TheincreasemagnitudeintheeastofSichuanBasin,thesouthofHengduanMountainandtheeastofGuizhouPlateauismuchwider,whilethestationswithprecipitationdecreasearedistributedinthesouthwestedgeofSichuanBasinandthewestofYunnanPlateau(Fig.3.8).Onthewhole,theregionsofprecipitationincreasearemainlyinhighaltitudearea,whilethesummerandwinterprecipitationinSichuanBasinandGuizhouPlateaualsoincreaseddistinctly.3.2.3TheSpatialDistributionofTemperatureandPrecipitationVariationinSummerMonsoonPeriodandWinterMonsoonPeriodThetemperaturesofabout90%ofthestationsinSouthwesternChinaisontheriseinsummermonsoonperiod,amongthem,thereareabout53%ofthestationswithsignificantwarmingwhicharemainlydistributedinXizangPlateau–HengduanMountainandYunnanPlateau.However,themoststationsinSichuanBasin,GuizhouPlateau,thecentralpartofHengduanMountainandthesoutheasternYunnanPlateaushowanonsignificantwarming.Moreover,thefourstationslocatedinthesoutheastofHengduanMountainoccurasignificanttemperaturedrop(Fig.3.9).Thetemperatureofabout94%ofthestationsinwintermonsoonperiodisontherise,andthestationswithsignificantwarmingaccountforabout68%oftotalstations.Differentfromthesummermonsoonperiod,theareawithsignificant 783SpatialandTemporalVariationofTemperature…Fig.3.9Spatialdistributionoftemperatureandprecipitationvariationinsummermonsoonperiodandwintermonsoonperiodduring1961–2008,asummermonsoonperiod,bwintermonsoonperiod,csummermonsoonperiod,dwintermonsoonperiodwarmingsharplyenlargeinwintermonsoonperiod.ThestationwithnonsignificanttemperatureincreaseordecreasearemainlydistributedinthecentralpartofSichuanBasin,thesouthernGuizhouPlateauandthesoutheastofYunnanPlateau(Fig.3.9).Themonsoonprecipitationofabout50%ofthestationsshowanincreasingtrendwhicharemainlydistributedinXizangPlateau–HengduanMountainandthenorthofYunnanPlateau,andamongthesestations,only5%ofthestationssucceedinthesignificancetest.However,themoststationsinSichuanBasin,GuizhouPlateau,theeastandwestedgeofYunnanPlateaushowadownwardtrend.Amongthem,theprecipitationofsomestationsinthewestofSichuanBasinandthewestofGuizhouPlateausignificantlyreduce.Theprecipitationincreasemainlyhappensinhighaltitudearea(Fig.3.9).Comparedwithsummermonsoonperiod,theareaofpre-cipitationincreaseinwintermonsoonperiodexpands.About61%ofthestationshaveanapparentincreasemomentum,butonly23%ofthestationspassthesig-nificancetestwhichareconcentratedinXizangPlateauandHengduanMountain.Inaddition,theprecipitationofalmostallthestationsinYunnanPlateauincreases.Onthecontrary,almostallthestationsinGuizhouPlateau,moststationsintheSichuanBasinandsomestationsinYunnanPlateaushowadeclinetrendinprecipitation.Amongthem,themagnitudeofreductioniswidestinGuizhouPlateau(Fig.3.9). 3.3DrivingMechanismforTemperatureandPrecipitation793.3DrivingMechanismforTemperatureandPrecipitation3.3.1TheRelationshipofTemperatureandPrecipitationVariationwithElevationBasedontheanalysisonmonthlymeanminimumtemperatureofQinghai–XizangPlateauandtheareasarounditin1961–2006,aconclusioncanbemadethatthewarmingmagnitudeofhightaltitudeareasismuchwider(Liuetal.2009),andthisfactalsoisfoundduringtheresearchontheclimatechangeinSwissareasandRockyMountains(BenistonandRebetez1996;FyfeandFlato1999).AswhattheFig.3.10shows,thereareagreatpositivecorrelationbetweenthemagnitudeofannualmeantemperaturechangesofallstationsinSouthwesternChinaandtheelevation,whichsuggeststhatthewarmingmagnitudewillincreaseastheriseofelevation.Thecorrelationvaluesbetweenthemagnitudeofspring,summer,autumnandwintertemperaturechangeandtheelevationare0.25,0.46,0.36and0.33.Thewarmingmagnitudeincreasesastheriseofelevationinsummer,autumnandwinterexceptforspring.Amongthesethreeseasons,thesignificanceofthewarmingmagnitudeinsummerisbiggestfollowedbyautumn(Fig.3.9).ThemagnitudeoftemperaturechangesinsummermonsoonandwintermonsoonperiodofallstationsinSouthwesternChinaandtheelevationalsohasapositivecorrelationwiththeelevation,andthecorrelationvaluesare0.43and0.50.Moreover,theelevationeffectofwarmingisquitesignificant(Fig.3.10).AsshownbyTable3.2,intermsofthemaximumwarmingmagnitudeindifferentaltitudes,theannual,spring,summer,autumn,winter,summermonsoonandwintermonsoonmaximumwarmingmag-nituderespectivelyoccurinthealtitudeof3,500–4,000,4,000–4,500,3,500–4,000,4,500–5,000,2,000–2,500,4,500–5,000and4,000–4,500m.Allhappeninthealtitudeofabove3,500mexceptforwinterone.Accordingly,theminimumwarmingmagnituderespectivelyoccurinthealtitudeof1,000–1,500,1,000–1,500,0–500,2,500–3,000,500–1,000,0–500,and0–500m.Amongthem,allhappeninthealtitudeofbelow1,500mexceptforautumnone.Thenumberofstations,ofwhichthemagnitudeoftemperaturechangesindifferentaltitudessucceedinthesignificancetest,alsoreflectthesignificantwarmingathighaltitude.Thethreestationsinthealtitudeof4,500–5,000mhaveasignificantwarming.Thesixstationsinthealtitudeof4,000–4,500malsoshowasignificantwarmingexceptforonestationinsummerandtwostationsinwinter.Theannualandeachseasonaltemperatureofeightstationsinthealtitudeof3,500–4,000misonanobviousrise.Intheelevationof3,000–3,500m,thereonlyannualandwintertemperatureofninestationssignificantrise,andthetemperatureofsevenandeightstationschangewarmerinsummerandwintermonsoonperiod,whilejustfourstationswarminspring.Thereareninestationinthealtitudeof2,500–3,000mshowingsignificantwarmingtrendinwintermonsoonperiod,whilealltherearehalfofstationswhichfailtopassthesignificancetestinspring,autumnandsummermonsoonperiod.Thesixofsevenstationslocatedinanaltitudeof2,000–2,500mshowasignificantwarmingtrendinautumnandthewinter 803SpatialandTemporalVariationofTemperature…Fig.3.10Therelationshipoftemperatureandprecipitationvariationwithelevationduring1961–2008monsoonperiod,andthereisonlyoneinwinter.Thereareonlyhalfof16stationslocatedinanaltitudeof1,500–2,000mheatingupinayear,winterandsummermonsoonperiod,whilethereareonlysixstationwarmingobviously.Therearesevenstationsinanaltitudeof1,000–1,500m,ofwhichthetemperaturerisesignificantlyinspring,andthenumberofstationsinanaltitudeof1,000–1,500m 3.3DrivingMechanismforTemperatureandPrecipitation81Table3.2Trendmagnitudesoftemperatureandprecipitationvariationindifferentaltitudesrank(°Cormm/10a)Altitude(m)NumberAnnualSpringSummerAutumnWinterWinterSummer(°C)(°C)(°C)(°C)(°C)monsoonmonsoon(°C)(°C)4,500–5,00030.420.310.210.420.7430.000.264,000–4,50060.340.330.230.350.430.390.283,500–4,00080.580.270.240.320.410.380.253,000–3,50090.380.180.210.220.370.280.182,500–3,00090.140.090.120.130.270.210.092,000–2,50070.240.160.200.240.780.350.161,500–2,000160.160.060.110.150.250.230.071,000–1,500160.01−0.180.080.160.190.170.08500–1,000170.170.120.060.14−0.040.190.080–500190.090.05−0.080.150.120.120.06Altitude(m)NumberAnnualSpringSummerAutumnWinterWinterSummer(mm/(mm/(mm/(mm/(mm/(mm/10a)(mm/10a)10a)10a)10a)10a)10a)monsoonmonsoon4,500–5,000318.705.424.373.241.232.9315.754,000–4,50063.853.711.99−0.181.463.292.153,500–4,00089.886.301.183.450.654.509.983,000–3,5009−3.975.61−7.86−2.260.424.06−7.802,500–3,000917.358.205.432.671.059.1012.792,000–2,5007−0.383.73−2.91−2.611.562.44−2.781,500–2,000161.919.31−7.80−4.841.843.40−3.041,000–1,50016−4.824.25−0.77−7.901.38−2.68−1.10500–1,00017−18.34−2.91−9.85−9.210.42−5.90−17.220–50019−17.88−5.476.74−18.662.06−2.24−13.422whichshowasharpwarmingtrendinayear,summerandsummermonsoonperiodare12.Theremorethantenstationspresentawarmingtrendinayear,autumn,winter,summermonsoonandwintermonsoonperiodamong17stationinanaltitudeof500–1,000m.Andthereare11stationswarmingsignificantlyinautumnamong19stationsinanaltitudeof0–500m.TheclimatecorrelationanalysisindicatesthattheregionswithawidermagnitudeofwarminginSouthwesternChinaaremainlylocatedaboveanaltitudeof3,500m.SomeexistingresearchesbelievethattherearethreepossiblereasonsofsignificantwarminginthehighaltitudeareasofQinghai–XizangPlateauinChina.(1)ThevariationofcloudcoverispossibletohavesignificanteffectsontherecentclimatewarmingofQinghai-XizangPlateau.Thereflectionandscatteringofthecloudabatealongwiththesignificantincreaseoflowcloudcoveratnight,whichwillleadtomoreheatabsorbedbygroundsurfaceandcausesharplywarming.Inaddition,thetotalcloudcoverandlowcloudcoverareyearlytodecreaseduringtheday,whichalsoleadtomoresolardirectradiationabsorbedbygroundsurfaceandthusacceleratethesurfacewarming(DuanandWu2006).Moreover,thestudyofTangetal.(2009)alsoconfirmsthattheannualtotalcloudcoverofmostareasofXizangAutonomousRegionwasonasignificantdeclinetrendin1971–2008.Thereinto,thereducingmagnitudeofthecentralwestpartofNaqu,reaching2.32%/10a,butthetotalcloud 823SpatialandTemporalVariationofTemperature…coverofsouthernedgeofXizangAutonomousRegionhasanonsignificantdecreasetrend.Thetotalcloudcoverispositivelycorrelatedwithprecipitationandrelativehumidity,andnegativelycorrelatedwithsunshinehours,meantemperatureanddiurnaltemperaturerange.Thesetwocorrelationsreflectthesignificantroleofcloudcovertotemperaturechanges.(2)Thepositivefeedbackofsnow/icealbedoisalsoconsideredasoneofthefactorscausingclimatewarmingoftheplateaubecausetheplateauisoneofthemostsensitivesnowfeedbackareasontheearth.Withtheclimatewarmingoftheplateau,seasonalsnowandicemeltingonthegroundsurfaceactsinadvance,whichwillcausethereductionofsurfacealbedoandmoreabsorptionofsolarradiation,andthencausethefurthermeltingofsurfacesnow.Thispositivefeedbackprocessofsnow/icealbedoalsoacceleratesthewarmingofplateau(LiuandChen2000).(3)Thethickeningofdirtonthesurfaceofsnowandiceortheincreaseofdustdensityinthehighaltitudeareawillmakethesnowandicealbedoreduceandthenresultintheincreaseofradiationandtemperature,whichalsoisoneofthefactorsofsignificantwarminginthehighaltitudearea.TheresearchofQianetal.(2011)hasproventhattheblackcarbonaerosolhasanobviouscontributiononreducingtheiceandsnowalbedoandincreasingsolarradiation.AstheFig.3.11shows,thereisapositivecorrelativitywiththemagnitudeofannualprecipitationchangeofallstationsinSouthwesternChinaandaltitude.Thecorrelationvalueis0.41,whichindicatesthatthemagnitudeofprecipitationincreasewidenwiththeriseofaltitude.Thecorrelationvalueswiththemagnitudeoffourseasonsprecipitationandthealtituderespectivelyare0.31,0.02,0.51and−0.08.Thereinto,thechangingmagnitudeincreaseswiththeriseofaltitudeinspringandautumn,butthechangingmagnitudedecreaseswiththeriseofaltitudeinwinter(Fig.3.11).ThemagnitudesofprecipitationchangeofallstationsinsummerFig.3.11Differenceofannualnetlongwaveradiationfluxatsurfacebetween1961–1985and1986–2008 3.3DrivingMechanismforTemperatureandPrecipitation83monsoonandwintermonsoonperiodhavethepositivecorrelationwiththealtitude,whichreflectsasignificantaltitudeeffect(Fig.3.11).AsshownbyTable3.3,themaximummagnitudesofprecipitationchangeinayear,spring,summer,autumn,winter,summermonsoonandwintermonsoonperiodoccurinthealtitudeof4,500–5,000,1,500–2,000,0–500,3,500–4,000,0–500,2,500–3,000and4,500–5000m.Theminimummagnitudesofprecipitationchangeinayear,sum-mer,winter,summermonsoonandwintermonsoonperiodoccurinthealtitudeof500–1,000m,andthespringandautumnminimummagnitudesoccurinthealtitudeof0–500m,whichconfirmsthattheprecipitationdecreasemainlyhappeninlowaltitudeareas;morealtitudeshavetheprecipitationdecreaseinautumnandsum-mer,butmorealtitudeshavetheprecipitationincreaseinwinterandspring.Comparedwiththetemperature,themagnitudeofprecipitationchangeoflessstationscanpassthesignificancetestindifferentaltitudes.Themagnitudeofpre-cipitationchangeofthreestationslocatedin4,500–5,000misonlynotsignificantinsummerandautumn,butsignificanttoincreaseinotherseasons.Therearehalfofstationsinaltitudeof4,000–4,500mshowingasignificantincreaseinwinterandwintermonsoonperiod.Butinthealtitudeof2,500–3,500m,therearemorethanhalfofstationsareontheriseinwintermonsoonperiod.Therearesomestationslocatedinthealtitudeof500–2,500mpassingthesignificancetestinspring.Andthereareeightofnineteenstationsin0–500mshowingasignificantdecrease.Tosumup,comparedwithtemperature,thealtitudeeffectissmaller,butthefactalsoisconfirmedthattheprecipitationathighaltitudeareasincrease.Inordertofurtheranalyzetheinfluenceoftopographicaltypeswherethemete-orologicalstationsarelocatedinontheobservationdataoftheannualmeantem-peratureandprecipitation,the110stationswereclassifiedintofourtopographictypes:summitstation,intermontanestation,flatstationandvalleystation.Theairfreedomofflatstationismaximum;valleystationhasanuniquevalleywindsystem,whereairflowmovementishamperedlarger;thewindspeedofsummitstationisstrongest.Thesefeatureswillhaveobviousinfluenceonthevariationmagnitudeoftemperatureandprecipitation.AsshowninTable3.3,thevariationmagnitudesofannualandwintertemperatureofintermontanestationarebiggerthanothertypesofstations.While,thevariationmagnitudesofflatstationsinspring,summer,autumn,winter,summermonsoonandwintermonsoonperiodarebiggest.Onthewhole,thewarmingmagnitudedeclinesgraduallyastheorderofflatstation,intermontanestation,valleystationandsummitstation.Onthecontrary,theflatandopennessofterraindecreasesuccessively.Intermsofprecipitation,themaximumreductionmagnitudeofannualsequencestandsinsummitstation,andthewinter,summer,autumnandsummermonsoonprecipitationalsoshowasametrend.Theminimumincreasemagnitudesinspringandwintermonsoonareinflatstation,butthemaxi-mumincreasemagnitudesinayear,winter,spring,autumn,summermonsoonandwintermonsoonstandinvalleystation.Andthesummerprecipitationofintermon-tanestationshowsaincreasetrend.Thesecharacteristicsalsoreflectstheobviousimpactofterrainonprecipitation.Allinall,theregionalterrainhasaobviousinfluenceintheobservationresultoftemperatureandprecipitation.Therefore,itisverynecessarytoconsidertheinfluenceofterrainintheclimatechangeresearch. 843SpatialandTemporalVariationofTemperature…Table3.3Meantrendmagnitudesoftemperatureandprecipitationindifferingtopographicaltypes(°Cormm/10a)TemperatureNumberAnnualWinterSpringSummerAutumnWinterSummermonsoonmonsoonSummit20.170.270.090.110.190.220.10stationIntermontane330.240.420.150.100.230.290.13stationFlatstation400.230.360.170.160.270.330.18Valleystation350.230.170.100.140.190.240.13PrecipitationNumberAnnualWinterSpringSummerAutumnWinterSummermonsoonmonsoonSummit2−24.95−1.444.51−19.88−8.871.4625.88stationIntermontane331.930.582.583.27−4.820.641.70stationFlatstation40−7.731.511.082.02−6.930.41−6.03Valleystation357.532.128.03−3.05−0.555.021.763.3.2TheCorrelationwithTemperatureVariation,Radiation,SeaSurfaceTemperatureandSunshineHoursAsshowninTable3.4,afterthemidof1980s,theannualandseasonaltemperatureinSouthwesternChinawarmedacceleratedly,andannual,spring,summermonsoonandwintermonsoontemperaturesin1961–1985presentedaweakdeclinetrend.TheannualandseasonaltemperaturesofXizangPlateau–HengduanMountainin1961–1985wasonthenon-significantrise,butthewarmingmagnitudein1986–2008enlargedobviously.In1961–1985,thetemperatureofYunnan–Guiz-houPlateauinayearandotherseasonsdecreasedorincreasedslightlyexceptthatitincreasedsharplyinsummer.Whileitwarmedbyalargemarginineveryperiod.ThetemperatureofSichuanBasinin1961–1985hadadownwardtrend,andtheannualandspringtemperaturedecreasesignificantly.Butithadasignificantwarmingineveryperiodexceptforwinter,andthewarmingmagnitudewashigherthanthatofwholeSouthwesternChina,Yunnan–GuizhouPlateauandXizangPlateau–HengduanMountain.AsshowninFig.3.11,comparedwith1961–1985,netlongwaveradiationfluxofSouthwesternChinaexceptforSichuanBasinincreasesremarkablyfrom1986to2008,whichreflectsthatthestrengthofairorgroundheatingprocessgraduallyincreased,andeventuallycausestemperaturerise.FurtheranalysisfoundthatthecorrelationwithannualmeantemperatureandseasurfacetemperatureofthewesternPacificOceanin1986–2008ishigherthan1961–1985,whichsuggeststheobviouscontributionofoceanthermalprocessstrengtheninggraduallytosignifi-cantregionwarming.Butthespecificmechanismofthiscontributionstillneedtofurtheranalyze(Fig.3.12).Theseasonofthemaximumwarmingmagnitudewas 3.3DrivingMechanismforTemperatureandPrecipitation85Table3.4Meantrendmagnitudesoftemperatureduring1961–1985and1986–2008inSouthwesternChina(°C/10a)YearsAnnualSpringSummerAutumnWinterWinterSummermonsoonmonsoonSouthwestern1961–1985−0.03−0.110.070.070.03−0.001−0.003China1986–20080.720.670.350.610.300.560.591961–19850.230.140.200.150.150.190.13XPHM1986–20080.660.550.340.490.470.610.481961–1985−0.03−0.160.300.05−0.02−0.070.09YGP1986–20080.510.460.210.530.130.350.431961–1985−0.38−0.37−0.31−0.03−0.13−0.22−0.28SB1986–20080.961.000.520.800.210.700.86Valuesfortrendssignificantatthe5%levelaresetinboldautumnin1961–2008inresearchedareafollowedbywinter.Themaximumin1986–2008happenedinautumnandspring.WhilethegreatestwarminginChinaandallovertheworldmainlyoccurredinwinterandspring,whichreflectstheeffectofsnowareasathighaltitude.Itisworthnotingthatthehighaltitudeareainstudiedareaisquitewide.JustXizhangPlateauaccountsfor54.6%ofwholestudiedarea.Thelargersnowareasinwinterandspringbringhighalbedoofgroundsurfaceandfurtherresultinthereductionofsurfacenetradiation.However,thesnowareasisminimuminautumnratheritisJulythathadbeenconfirmedbyfieldstudy.Sothesnowandicealbedoislowinthistime,andthemoresolarradiationwouldbeabsorbedbygroundsurface.AsshowninTable3.5,onlyspringtemperaturein1961–2008inthestudiedarehadapositivecorrelationwithsunshinehours.Thecorrelationvalueofannual,springandsummertemperaturewithsunshinehoursin1961–1985hadpassedthesignificancetest,whileonlythepositivecorrelationvalueofsummertemperaturein1986–2008withsunshinehoursfailedtopassthesignificancetest.Itstatesthattheincreasingsunshinehourshasaobviouscontributiononacceleratedwarmingafterthemidof1980s.Intermsofthreesub-regionsincludingXizangPlateau–-HengduanMountain,Yunnan–GuizhouPlateauandSichuanBasin,theeffectofsunshinehourschangetothetemperaturechangeofSichuanBasinin1961–2008ismostsignificant.Thisfigurealsocanbeprovenbythesimilarchangetrendoftemperatureandsunshinehoursinthisarea(Fig.3.13).AndtheeffectinYun-nan–GuizhouPlateaumainlyhappenedinspringandwinter;theeffectinXizangPlateau–HengduanMountainmainlyoccurredinwinter(Table3.5).In1961–1985,therewasapositivecorrelationwithsunshinehourschangeandtheannualandseasonaltemperaturechangeofthesethreesub-regions,whichsuggeststhecom-moninfluenceofsunshinehoursontemperature.ThecorrelativitywithsunshinehourschangeandtemperaturechangeofYunnan–GuizhouPlateauandSichuanBasinwasrelativelysignificantduring1986–2008.Butthereonlywintertemper-aturehadasignificantpositivewithsunshinehourschangeinXizangPlateau–-HengduanMountain,andtheautumnsunshinehourshasanegativecorrelativitywiththetemperatureofYunnan–GuizhouPlateauandXizangPlateau–Hengduan 863SpatialandTemporalVariationofTemperature…Fig.3.12CorrelationfieldbetweenannualtemperatureseriesinSouthwesternChinaandannualseasurfacetemperaturein1961–1985(a)andin1986–2008(b)Mountain,whichindicatesthesunshinehourshasmoresignificantimpactinthetemperaturechangeatlowaltitude,andreflectstheregionaldifferenceofsunshinehourschangein1986–2008. 3.3DrivingMechanismforTemperatureandPrecipitation87Table3.5Correlationcoefficientsbetweentemperatureandsunshinehoursinthreesub-regionsofSouthwesternChinaYearsAnnualSpringSummerAutumnWinterSouthwesternChina1961–2008−0.090.440.240.020.161961–19850.480.660.730.0240.271986–20080.350.520.250.320.561961–20080.360.670.650.310.14SB1961–19850.770.660.860.320.251986–20080.660.790.630.440.581961–20080.040.500.190.100.38YGP1961–19850.450.650.65−0.070.501986–20080.490.540.0240.440.491961–2008−0.130.270.11−0.140.34XPHM1961–19850.370.610.540.250.441986–20080.10.170.20−0.170.47Valuesfortrendssignificantatthe5%levelaresetinboldFig.3.13Inter-annualvariationbetweenannualmeantemperatureandsunshinehoursduring1961–2008inSichuanbasin3.3.3TheCorrelationofTemperatureandPrecipitationVariationandAtmosphericCirculationInordertoexaminetheinfluenceofatmosphericcirculationvariationontemper-aturechangeinstudiedarea,thisstudyanalyzethecorrelationwithspringandwintertemperatureandsea-levelpressureof0–70and30–170°N.AsshowninFig.3.14,thesummertemperaturehasapositivecorrelativitywiththesealevel 883SpatialandTemporalVariationofTemperature…Fig.3.14CorrelationfieldsbetweentheoveralltemperatureseriesinSouthwesternChinaandsealevelpressureinsummer(a)andwinter(b)during1961–2007.ReprintedbypermissionfromIOPPublishing:Ref.(Lietal.2011).Copyright(1993)pressureofMongoliaregion(LakeBaikal),thesouthpartofQinghai–XizangPlateauandthenorthpartofsouthwestAsia,whichsuggeststhatthesealevelpressureofaboveregionshaveanobviousimpactonthesummertemperature 3.3DrivingMechanismforTemperatureandPrecipitation89increase.ThewintertemperatureofstudiedareashowsanegativecorrelationwiththesealevelpressureofMongoliaregion,SoutheasternChina,thenorthpartofQinghai–XizangPlateau,andasignificantlypositivecorrelationwithCentralAsia,EuropeanregionsandthesouthpartofQinghai–XizangPlateau.Thereinto,asignificantnegativecorrelationwiththesealevelsurfaceofthenorthpartofQinghai–XizangPlateauhasbeenshown.ThisindicatesthatthewintertemperatureriseisassociatedwiththeriseofsealevelpressureofMongoliaregion,South-easternChina,andthenorthpartofQinghai–XizangPlateauaswellasthereductionofCentralAsia,EuropeanregionsandthesouthpartofQinghai–XizangPlateau.Basedonthispoint,thisstudymapstwocirculationcompositeimagesofsummerandwinterorextremehightemperatureyearandextremelowtemperatureyearbymeansofNCEP/NCARreanalysisdata,andarrivesatthecirculationchangesinthesetwospecialperiodsthroughallextremehightemperatureyearsminusallextremelowtemperatureyears.Fromthedeviationphotoofstronglypositiveandnegativetemperatureinsummer(Fig.3.15),astrongcyclonecirculationisformedinNorthernChinawithcenteredbytheLakeBaikalat500hpaandhasbeenanimportantcirculationsystemofEurasia.Thebiggestdifferenceofgeopotentialheight(about−25gpm)appearsinaroundLakeBaikalwhichcenterisnear50°Nand110°E.Thecom-positeimagesofgeopotentialheightat300hpaalsoshowssimilarfeaturesandthemaximumdifferenceofgeopotentialheightisabout−10gpm.Atthesametime,therearetwoanticycloniccirculationsformedonbothsidesofcyclonesystem,whichcentersrespectivelyin50°Nand40°E,50°Nand160°E.Inaddition,twoanomalousanticycloniccirculationsalsoforminWesternandEasternChinawhichcentersrespectivelyin35°Nand80°E,45°Nand120°E.ThegeopotentialheightdifferenceismuchlargerinthesetwoareasinChina.Ontheonehand,thischangeofcirculationreflectstheweakeningofAsianmonsoonsystemandleadtothestrengtheningofnorthwestwindinthenorthandeastoftheQinghai–XizangPlateau.Ontheotherhand,theanticycloneinEasternChinahasnotonlyhinderedthemovingofseawarmcurrenttowardsnorth,alsogreatlycompressedtheinflu-encerangeofseawarmcurrentandeventuallymadethestudiedareasdominatedbyprevailingnortheastwind.Thereby,themovingofIndianmonsoonandanyairflowfromsouthofoceanareweakenedtowardsnorthandthestudiedareaiscontrolledbytheanticyclonesystem.Therefore,theinfluenceoftwoanomalousanticycloniccirculationsonstronglypositivetemperatureinsummersinSouthwesternChinahasresultedinxerothermicnorthwestwindformedinthenorthofQinghai–XizangPlateau.Moreover,thenortheastairflowresultedfromanticycloneinEasternChinamovestowardssouthpassesHengduanMountains,SichuanBasinandYunnan–-GuizhouPlateauandfinallyarrivesatXizangPlateau.Thisnortherlyaircurrentblocksthetransportofwatervaporfromtheoceantonorthandmakesthestudiedareacontrolledbyxerothermicairmass.Tosomeextent,thesecirculationback-groundsexplainwhyairtemperatureincreasesandtherainfalldecreasesinsummerinthestudyarea.AsshowninFig.3.16a,thereisananomalyenhancedcyclonecirculationatnear50°Nand45°E(centralAsiaandEurope),ofwhichmaximumdeviationsofgeopotentialheightisabout−80gpm.Itcausesthattheanticyclonic 903SpatialandTemporalVariationofTemperature…Fig.3.15Differencesbetweenmeangeopotentialheightandwindfieldatthe500hPa(a)and300hPa(b)insummerswithstronglypositiveandnegativetemperaturedeviationsexceeding±1σofthe1961–2008mean 3.3DrivingMechanismforTemperatureandPrecipitation91Fig.3.16Differencesbetweenmeangeopotentialheightandwindfieldatthe500hPa(a)and300hPa(b)inwinterswithstronglypositiveandnegativetemperaturedeviationsexceeding±1σofthe1961–2008mean 923SpatialandTemporalVariationofTemperature…circulationofEurasiacenteredbynear40°Nand120°EpresentsaweakeningtrendandmakethecentermovetowardssouthandarriveatNorthChina.Thiscirculationformisconsistentwiththecompositeimageofgeopotentialheightat300hPa(Fig.3.16).Ontheonehand,theabovecirculationbackgroundsshowthestrengtheningofwestwindcirculationinsummerswithstronglypositivetemper-ature.Ontheotherhand,thedeviationsbetweenwinteranticycloniccirculationandcycloniccirculationhasbeenstrengthenedanddevelopedsouthwestwindinNorthernChina,whichweakensthestrengthofwintermonsoon,limitsitsstretchingtosouthandreducestherateofwintercoldwave.Thestudiedareasalsosuffertheeffectofsoutheastwarmwetaircurrentfromtheseaandthesecirculationbackgroundsarehelpfultothewinterwarming.Thisstudycalculatestheaverageofwatervaporfluxinsummerandwinterof1961–2008byusingtheNCEP/NCARreanalysisdataandarrivesatthedifferenceofboththewatervaporfluxesthroughdryyearsminuswetyearssoastofurtherunderstandtheinfluenceofcirculationsystemontheprecipitationchange.AsshowninFig.3.17,whetherinwinterorsummer,themaximummeanwatervaporfluxfrom1961to2008inSouthernChinaalwaysisinthehighaltitudeareacenteredbyXizangPlateau,whichindicatestheabundantwatervaportransportinthisregion,andwhichmaybeoneofreasonsthattheprecipitationincreaseinthestudiedareaaremainlyinthehighaltitudearea.ThedifferenceofwatervaporfluxofSouthChinabetweeninwetyearsanddryyearsisverysmall,whichindicatesthevaporfluxslightlychangesinthesetwoperiods.ButthewatervaporfluxinwetyearsisslightlyhigherthanindryyearsintheeastandwestofXizangPlateau,thesouthofHengduanMountainandYunnanPlateau(Fig.3.18).Thesecharacteristicsprovethatthewatervaportransportofthestudiedareahasnoobviousinterannualdifference,indicatethedifferenceofwetyearanddryyearisnotcausedbythechangesofwatervaportransportandmakesurethenon-significantchangetrendofrainfallinstudiedarea.ThechangeofthewesternPacificsubtropicalhighisregardedasoneofthemainfactorsimpactingprecipitationchangeinChina,andthestrengthofthewesternPacificsubtropicalhighgraduallyincreasedinrecentyears.AsshowninTable3.6,thewinterprecipitationofSouthwesternChina,XizangPlateauandHengduanMountainhasasignificantpositivecorrelationwiththestrengthandareaindexofthewesternPacificsubtropicalhigh,andalsoshowsapositivecorrelationwithprecipitationofYunnan-GuizhouPlateau,whichreflectsthesignificantcontributionofenhancementofthewesternPacificsubtropicalhighonwinterprecipitationincrease.ThepossiblemechanismistheenhancementofthewesternPacificsubtropicalhighinwinterwillcontributetothetransportofoceanwarmairflowtomainland,thuscausetheprecipitationevent.TheenhancedwesternPacificsubtropicalhighpresentsanobviousnegativecorrelationwiththeannualandspringprecipitationofYunnan-GuizhouPlateau,aswellasasignificantlynegativecorrelationwithautumnprecipitationofSichuanBasin.BecausethestretchingofwesternPacificsubtropicalhightowardswestafterstrengtheninginsummerandautumnwillmakethestudiedareacontrolledbydryairandeventuallyleadtotemperaturerisebutprecipitationreduction. 3.3DrivingMechanismforTemperatureandPrecipitation93Fig.3.17Themeanwatervaporfluxat500hPainsummers(a)andwinters(b)during1961–2008 943SpatialandTemporalVariationofTemperature…Fig.3.18Differencesbetweenmeanwatervaporfluxat500hPainsummers(a)andwinters(b)withstronglypositiveandnegativetemperaturedeviationsexceeding±0.5σofthe1961–2008meanTable3.6ThecorrelationbetweenprecipitationandWesternPacificsubtropicalhighindexRegionsIndexAnnualSpringSummerAutumnWinterSouthernChinaStrength0.130.090.080.090.55Area0.130.120.030.070.59XPHMStrength0.130.090.080.090.55Area0.130.120.030.070.59YGPStrength−0.26−0.26−0.030.020.26Area−0.31−0.210.06−0.080.21SBStrength−0.08−0.20.24−0.330.17Area−0.16−0.190.17−0.440.13Valuesfortrendssignificantatthe5%levelaresetinbold3.3.4TheComparisonofVariationMagnitudeofTemperatureinUrbanandRuralStationsAtpresent,mostoftheresearchesthinkthatclimatewarmingcanbeattributedtotheincreasedconcentrationsofgreenhousegases(IPCC2007).However,thelong-termsurfacewarmingmayalsobeassociatedwithotherclimatefactors,forexample,theimpactofurbanheatislandeffect(Zhouetal.2004).Cityheatislandeffectisoneofthehumanfactorswhichhaveimportanteffectsonclimatechange.Thesurfaceconditionandcirculationcharacteristicsofthecityaredramaticallychangedduetothelandusechangecausedbyurbanization,whichresultsinthechangeofpowerbalance,powerbalanceandwaterbalance,andeventualformationoftheobviouscitymicroclimate(Morrisetal.2001).Inordertoanalyzethedifferencebetweenurbanandruralstations,the110meteorologicalobservationstationshavebeendivided58urbanstationsand52ruralstations.Theresultsindicatethatthemeantemperatureoftheruralstationsof83%andtheurban 3.3DrivingMechanismforTemperatureandPrecipitation95stationsof76%presentaincreasetrend;thetemperatureoftheruralstationsof38,47,67,52,62,52%andtheurbanstationsof58,67,67,67,79and69%allhavebeenontheriseinspring,summer,autumn,winter,summermonsoonandwintermonsoonperiod.Therearemoreunbanstationswarminginautumnandtherearemoreruralstationswarminginwinter.Themoreobviousthingisthatthemagni-tudesofannualandseasonaltemperaturechangeinruralstationarehigherthantheurbanstations(Fig.3.19).Fig.3.19Inter-annualvariationoftemperatureinurbanandruralstationsduring1961–2008 963SpatialandTemporalVariationofTemperature…AstheFig.3.19shows,thetemperatureofruralstationshasacontinuousincrease,whereasthetemperatureofurbanstationsappearedadecreasein1960s,thenslowlyriseduring1970–1985andfinallysignificantlyriseduringthefol-lowingtime.Thetemperatureofruralstationsiscontinuoustoriseinspring,butthetemperatureofurbanstationsdeclinebefore1985andthenrise.Allinall,theobvioustrendvariationofurbanstationsisalargertemperatureincreaseafterthemidof1980s,whiletheruralstationsshowacontinuoustemperaturerise.Ingeneral,thedeviationsofmagnitudeoftemperaturechangebetweenurbanstationsandruralstationsisdefinedasthecontributionofurbanheatislandeffect(Jonesetal.2008;Renetal.2008).Ifthiscouldbelookedasabasis,theurbanheatislandwouldnothaveasignificantcontributiontothemeantemperaturechangeofurbanstationsinstudiedarea.Thisreasoningmaybeexplainedbyfollowingthreeaspects:(1)theeffectofaltitudeexplainsthedramaticalwarminghappenedinruralstations,andthemagnitudeoftemperaturechangeinstudiedareashowsatrendofincreasingwiththeriseofaltitude.Themeanaltitudeofurbanandruralstationare1,156and1,692m,respectively.ThereisonlyoneurbanstationinXizangPlateauandtwourbanstationsinHengduanMountain.TheallrestofurbanstationsarelocatedinYunnan–GuizhouPlateauandSichuanBasin.Inaddition,thechangetrendoftheannualmeantemperatureinurbanstationsissimilartothatofYun-nan–GuizhouPlateauandSichuanBasin,whichalsoconfirmedtheabovereasoning(Fig.3.20).(2)Theurbanheatislandeffectmainlyinfluenceextremetemperature,especiallytheextrememinimumtemperature,whichwillbeanalyzeddetailedlyinChap.4.(3)Asthestudiedareaislowerinurbanizationrate,thereareonlythreestationsinmegacitieswherethepopulationismorethanmillionsamong58selectedurbanstations.Additionally,theresomeresearcheshaveproventhatinmegacities,forexample,Seoul,thecapitalofSouthKorea,theurbanheatislandeffectresultedinthattheannualmeantemperatureincrease0.56°Cduring1973–2006(KimandBaik2002).TherelatedresearchesinChinaalsohaveconfirmedthatthesignificantaffectoftheurbanheatislandtoannualmeantemperaturemainlyoccursinme-gacitieslikeBeijing,Shanghaietc.Moreover,thestudyofTangetal.(2008)hasdemonstratedthattheurbanheatislandeffecthasaslightinfluenceontheFig.3.20Inter-annualvariationoftemperatureinYunnan-GuizhouplateauandSichuanbasinduring1961–2008 3.3DrivingMechanismforTemperatureandPrecipitation97observationstationinSichuan,Yunnan,GuizhouandChongqingbecauseofthelowerurbanizationlevel.Tosumup,thealtitudeisthemainreasonresultinginthedifferenceinthemagnitudeoftemperaturechange.3.4SummaryThischapterfocusesontheanalysisofpartialandtemporalvariationsofannualmeantemperatureandprecipitationaswellasitspossibleinfluencingfactorsbymeansofthemeteorologicaldataof110stations.Themainfindsofthechapterareasfollows:(1)Thetemperaturesignificantlyraised,andtheprecipitationshowedastabletrend.In1961–2008,theannualmeantemperaturewas12.7°Candtheannualmeanprecipitationwas965mm.Thespatialdistributionofthetemperatureandprecipitationshowedagradualdeclinetrendfromsouthwesttonortheast.Nearly50years,annualaveragetemperaturesignificantlywarmedandthemagnitudewas0.33°C/10a.Themagnitudeoftemperatureriseenlargedobviouslyafter1980sratherthanasmallmagnitudebefore1980s.Thesea-sonaltemperaturechangealsoreflectsthesignificantwarmingtrend.Theannualprecipitationinthestudiedareashowedaslightreductionnon-statisticssignificancefrom1961to2008andthemagnitudeofchangewas−0.006mm/10a.Theprecipitationremainedstablein1961–1980,thenitslowlydeclinedinthewhole1980sandincreasedobviouslyin1990s.Buttheprecipitationshowedawavelikedecreasechangeaftersteppingintonewcentury,thereinto,thespingandwinterprecipitationincreaseobviously.(2)Thewarmingandprecipitationincreasinginthehighaltitudeareawasmoreapparent.Theannualmeantemperatureofstationsofabout77%instudiedareasignificantlyincreased.Onthewhole,thestationswithsignificantandwidermarginofwarmingweremainlydistributedinXizangPlateau,Hengd-uanMountainandYunnanPlateau,andthestationswithnon-significantincreaseanddecreaseweremainlydistributedinSichuanBasinandGuizhouPlateau,ofwhichthemagnitudeoftemperatureincreaserosesignificantlywiththerisingofelevation.Inaddition,themagnitudeofwarmingfellsuccessivelyintheorderofflatstation,intermontanestation,valleystation,andsummitstation.Thesignificancelevelofprecipitationchangeisextremelylowandtheannualprecipitationstationsofonly5%increasedsignificantly.ThestationswithprecipitationincreasearemainlydistributedinXizangPlateau,HengduanMountainandthecentralandnorthwestofYunnan–GuizhouPlateau,whilethestationswithprecipitationdecreasearemainlylocatedintheeasternpartofYunnanPlateau,GuizhouPlateauandSichuanBasin.Moreover,thestationswithwidermarginofsignificantdecreasearemainlydistributedinsurroundingSichuanBasin.Fromthispoint,thecharacteristicofprecipitationincreaseat 983SpatialandTemporalVariationofTemperature…highaltitudeandprecipitationdecreaseatlowaltitudehasbeenpresented.Themaximummagnitudeofdecreasingoccurredinsummitstationsandthemax-imummagnitudeofincreasehappenedinvallystation.(3)Therearemanycausesofsignificantwarmingafterthemidof1980s.Com-paredwiththe1961–1985,thenetlongwaveradiationfluxreceivedbygroundsurfaceincreasedsignificantlyfrom1986to2008,whichindicatesthatthestrengthofatmosphericheatingprocesshasbeenincreasedgradually.ThecorrelationlevelwiththeannualaveragetemperatureofSouthwesternChinaandtheseasurfacetemperatureofthewesternPacificin1986–2008wassignificantlyhigherthanin1961–1985,whichreflectstheapparentcontribu-tionofgradualstrengtheningofoceanthermalprocesstosignificantwarminginthelatterperiod.Thesignificantlypositivecorrelationwiththetemperaturechangeandsunshinehoursduring1986–2008inthestudiedareareflectsitsapparentcontributiontotheacceleratedtemperatureriseafterthemidof1980s.Inaddition,theurbanstationismorethantheruralstationbothinthemagnitudeoftemperaturevariationsandthepercentageofstationsshowingsignificantwarming,whichisconsideredtobecausedbytheelevationdif-ferenceofdistributionofurbanstationandruralstation.(4)Theregionalwarmingisassociatedwiththechangeofatmosphericcirculationinthelargescale.Thestudiedareaisundertheinfluenceoftwoanomalousanticyclonicsinsummerswithstronglypositivetemperature,whichcausesthatthenortheastwindofHengduanMountain,Yunnan–GuizhouPlateauandSichuanBasinwouldblockthetransportoftheoceanwatervaportowardnorthmakesthestudiedareaunderthecontrolofdryandhotairmass.ThedifferencebetweenwinteranticycloniccirculationandcyclonecirculationfurtherstrengthensandformsthesouthwestwindinNorthernChina.Thenitweakensthestrengthofwintermonsooninturn,limitsitsstretchtosouth.Inaddition,itreducestherateofthecoldairlikewintercoldwaveandfurthercontributestothetemperatureriseinwinter.Thesecirculationbackgroundpartlyexplainedthesignificantwarminginthestudiedarea.(5)Thecorrelationwithprecipitationchangesandwatervaporfluxisweak.In1961–2008,themaximumsoftheaveragewatervaporfluxinwinterandsummerwerebothinthehighaltitudeareaofXizangPlateau,whichpartlyexplainedtheprecipitationincreaseinthisregion.Thedifferenceofvaporfluxinwinterofdryyearsandwetyearsisverysmall,whileinsummer,thevaporfluxesoftheeastandwestofXizangPlateau,thesouthofHengduanMountainandYunnanPlateauinwetyearsareslightlymorethanthedryyears.Thisdemonstratesthatwatervaportransporthasnoapparentinteran-nualvariationandconfirmstheweakcorrelationwiththeinterannualvari-abilityofprecipitationandwatervaporflux.ThewesternPacificsubtropicalhighhasanobviousinfluenceontheprecipitationchangeofresearchedarea.TheenhancementofwesternPacificsubtropicalhighinwinterishelpfultothetransportofwarmaircurrentfromoceanstothemainlandresultingin 3.4Summary99precipitationevents.However,thestretchofwesternPacificsubtropicalhighinsummerandautumntowardwesttothemainlandafterstrengtheningwillcausethestudiedareaiscontrolledbydryandwarmairmassandeventuallyleadtotemperatureincreaseandprecipitationdecrease.ReferencesBeniston,M.,&Rebetez,M.(1996).RegionalbehaviorofminimumtemperaturesinSwitzerlandfortheperiod1979–1993.TheoreticalandAppliedClimatology,53,231–243.Bian,D.,&Du,J.(2006).ClimatevariationfeatureanditseffectonenvironmentchangeincentralTibetfrom1961to2000.JournalofAppliedMeteorologicalScience,17(2),169–175.(inChinese).Chen,J.Q.,etal.(2008).Theinterannualandinterdecadalchangeofclimateduring1951–2000inSichuanBasin.JournalofChangjiangEngineeringVocationalCollege,25(3),23–25.(inChinese).Cheng,J.G.,&Xie,M.E.(2008).TheanalysisofregionalclimatechangefeaturesoverYunnaninrecent50years.AdvanceinEarthSciences,27(5),19–26.(inChinese).Dong,M.Y.&Wu,Z.F.(2008).AnalysisonthespatialandtemporalcharacteristicsoftemperaturechangeinNortheasternChinaoverthepast50years.GeologyJournals,30(7),1093–1199.(inChinese).Duan,A.M.,&Wu,G.X.(2006).ChangeofcloudamountandtheclimatewarmingontheTibetanPlateau.GeophysicalReseachLetters,33,L22704.Duan,K.Q.,etal.(2002).Responseofmonsoonrainfallonclimatewarmingfromtheglacieraccumulationinhimalayas.ChineseScienceBulletin,47(19),1058–1511.(inChinese).Duan,J.P.,etal.(2010).TemperaturevariabilitysinceA.D.1837inferredfromtree-ringmaximumdensityofabiesfabricinGonggamountains.ChineseScienceBulletin,55(11),1036–1042.(inChinese).Fan,Z.X.,etal.(2008).AnnualtemperaturereconstructioninthecentralHengduanMountains,China,asdeducedfromtreerings.InternationalJournalofClimatology,28,1879–1887.Fyfe,J.C.,&Flato,G.M.(1999).EnhancedclimatechangeanditsdetectionovertheRockyMountains.JournalofClimate,12,230–243.Hou,S.G,ZhangD.Q.(2003).Comparisonoftwoicecorerecordssince1954fromMt.Qomolangma(Everest)Region.JournalofGlaciologyandGeocryology.25(3):256–260.(inChinese).Hou,S.G.,etal.(2002).RecentchangeinicecoresaccumulationrateofQinghai-XizangPlateau.ChineseScienceBulletin,47(20),1588–1591.(inChinese).IntergovernmentalPanelonClimateChange(IPCC).(2007).Summaryforpolicymakers.InS.Solomonetal.(Eds.)ClimateChange2007:ThePhysicalScienceBasis.ContributionofWorkingGroupItotheFourthAssessmentReportoftheIntergovernmentalPanelonClimateChange(pp.1–13).Cambridge:CambridgeUniversityPress.Jia,W.X.,etal.(2008).TheregionaldifferenceandcatastropheofclimaticchangeinQilianMt.Region.JournalofGeographicalSciences,63(3),257–269.(inChinese).Jones,P.D.,etal.(2008).Urbanizationeffectsinlarge-scaletemperaturerecords,withanemphasisonChina.JournalGeophysicalResearch,113,D16132.Kang,S.C.,etal.(2000).TherecordoficecoreinfareastRongbukinthenorthslopeofhimalayas.JournalofGlaciologyandGeocryology,22(3),211–217.(inChinese).Kim,Y.H.,&Baik,J.J.(2002).MaximumurbanheatislandintensityinSeoul.JournalofAppliedMeteorology,41,651–659. 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Chapter4SpatialandTemporalVariationofClimateExtremesinSouthwesternChina4.1SpatialandTemporalVariationofClimateExtremes4.1.1SpatialandTemporalVariationofIndicesofTemperatureExtremesAsshowninFig.4.1,theannualmeanTX10,TN10,TXn,TNnandFDallshowedanupwardstrendin1961–2008inSouthwesternChinaexceptforID.TheannualmeansofID,TX10,TN10,TXn,TNnandFDare9.8d,16.5d,16.3d,1.7°C,−8.5°Cand74.5d,respectively(Table4.1).Thecolddayfrequency(TX10)reducedsignificantlyatarateofabout0.13d/10a.Theinterannualchangeshowedawavelikeincreasebeforethemidof1980sandadecreasefollowed(Fig.4.1).Therewerestationsofabout79%beingonthedeclineamong110stationsselected.Amongthem,themagnitudeofdeclineof36%hadpassedthesignificanttest(Table4.1).ThemagnitudeofTX10decreaseofstationsdistributedineastofXizangPlateauandHengduanMountainwaslargeandobviouslymorethanthatofstationsinYunnan–GuizhouPlateauandSichuanBasin.Additionally,TX10ofsomestationsintheeastofSichuanBasinandYunnanPlateauincreased(Fig.4.2).Thecoldnightfrequency(TN10)ofstudiedareasignificantlyreducedatarateofabout0.37d/10ain1961–2008,duringwhichtheTN10ofstationsofabout95%reducedandthemagnitudeofdeclineof91%hadpassedthesignificanttest.Thespatialdistributionshowsagradualreductiontrendfromhighaltitudeareatolowaltitudearea(Figs.4.1and4.2)Overall,thespatialdistributionofregionaltrendsofabovetwoindicesshowsagradualdeclinetrendofwarmingmagnitudefromwesttoeast,reflectsthesignificanteffectofelevation,andalsoconfirmsthatnightindexiswarmingbyawidermarginthandaytimeindex.Therethecoldestdaytemperature(TXn)from85%ofthestationsandthecoldestnighttemperature(TNn)from97%ofthestationsperformanincreasetrendduring1961–2008inSouthwesternChina.IntermsofTXn,theincreasetrendofonly24%ofthestationshavepassedthesignificancetest,andthesignificantlyincreaseof©Springer-VerlagBerlinHeidelberg2015101Z.Li,StudyonClimateChangeinSouthwesternChina,SpringerTheses,DOI10.1007/978-3-662-44742-0_4 1024SpatialandTemporalVariationofClimate…Fig.4.1Regionalannualanomalyseries,1961–2008,forindicesoftemperatureextremesabout77%ofthestationsinTNnconfirmsthattheminimumtemperatureiswarmingbyawidestmargin(Table4.1).TXnshowedareducingtrendbefore1980sandfluctuatedtorise,thenshowedawavelikedecreasechangeafter2000.Themagnitudeofchanging0.13°C/10a.WhileTNncontinuedtowarmatarateofabout0.29°C/10a.Bothmagnitudesofchangingaresuccessfulinsignificancetest,butthelatteroneistwotimesmorethantheformerone(Fig.4.1).ExceptforafewstationsinSichuanBasinandthesouthofHengduanMountainwhereTXnshowsadownwardtrend,TXninthemoststationsshowsaincreasingtrend.ThestationswithasignificantdecreasearemainlydistributedintheeastofXizangPlateauandthecentralofYunnan–GuizhouPlateau(Fig.4.2).ComparedwithTXn,TNnwarmuniversallyinSouthwesternChina(Fig.4.2).Duetothelowlatitudelocationofthestudyarea,there55stationshavenoicedays(ID),and6stationshavenofrostdays(FD).In1961–2008,theicedaysnon-significantlyreducedandthemagnitudeisverysmall(0.09d/10a).Itslowlyincreasedbefore1980,thengraduallyreducedafter1980.There15stationsdecreasedsignificantlywhicharemainlydistributedin 4.1SpatialandTemporalVariationofClimateExtremes103Table4.1TrendsperdecadeandpercentageofstationswithpositiveornegativetrendsforregionalindicesoftemperatureandprecipitationextremesinSouthwesternChinaduring1961–2008(°Cormmord/10a)IndexAveragesRegionalRangePercentagePercentagePercentagePercentagetrendsofstationsofstationsofstationsofstationsshowingshowingshowingshowingpositivesignificantnegativesignificanttrendpositivetrendnegativetrendtrendTX1016.5−0.13−11.3–1.37936TN1016.3−0.37−4.6–2.69591TXn1.70.13−0.3–0.98524TNn−8.20.29−0.1–2.09777ID9.8−0.09−5.7–0.48627FD74.5−0.29−21.2–09881DTR10.9−0.18−0.6–0.28250TN9016.10.36−3.6–10.49588TX9016.50.22−4.0–8.88862TXx31.10.11−0.4–0.88129TNx19.40.17−0.5–0.78067GSL301.00.12−2.2–14.09638PRCPTOT912.60.03−69.0–12.25725SDII9.10.03−0.3–0.55911RX1day66.80.05−7.6–10.86410R95238.20.04−37.3–39.16310R9974.00.05−19.3–24.6678RX5day116.60.03−11.5–12.7558CDD58.9−0.05−57.5–4.57428CWD8.4−0.08−1.7–1.07619R10mm27.40−2.1–3.85515R20mm10.70−1.1–1.1558R25mm7.90.02−0.9–1.16112Valuesfortrendssignificantatthe5%levelaresetinboldXizangPlateau.ButthefivestationsinYunnan–GuizhouPlateaushowedaincreasingtrend(Figs.4.1and4.2).Frostdayscontinuetodecreasesignificantlyatarateofabout0.29d/10a.Thereare98%ofthestationsperformingadownwardtrendandaround81%ofthestationspassedthesignificancetest.ThemagnitudeofdeclineofmoststationsinXizangPlateauandHengduanMountainaremorethantheYunnan–GuizhouPlateauandSichuanBasin,whilethestationswithnon-sig-nificantdecreasearemainlydistributedintheYunnan–GuizhouPlateau(Figs.4.1and4.2).Thediurnaltemperaturerangeisanimportantindicatorsofknowingclimateextremes.Liuetal.(2006)foundthatbothmaximumtemperatureandminimumtemperaturewereontheriseinrecentdecades,butthemagnitudeofwarmingofminimumtemperaturewasmorethanthatofthemaximumtemperaturewithresultinginthecontinuousdecreaseofthediurnaltemperaturerange.TheresearchofYouetal.(2008a,b)alsoconfirmedthischange.Inaddition,themagnitudeof 1044SpatialandTemporalVariationofClimate…Fig.4.2SpatialdistributionoftrendsperdecadeforTX10,TN10,TXn,TNn,ID,FD,DTR,TN90,TX90,TXx,TNxandGSLglobalminimumtemperaturerisealsomorethanthemaximumtemperature(Easterlingetal.2000).AconclusioncanbemadefromFig.4.1,theaverageofdiurnaltemperaturerangeofstudiedareafrom1961to2008was10.9°C,andtheannualdiurnaltemperaturerange(DTR)significantlyreducedatarateofabout0.18°C/10a.Itisinterestingthattheannualdiurnalrangecontinuedtodecreasebefore1990butfluctuatedtoincreaseafterwards(Fig.4.1).Abovechangewascausedbythevariationgapbetweenthewideningandnarrowingofregionaltrendsofthemaximumtemperatureinrecentyears.Thefurtheranalysisindicatedthatthemeanmaximumtemperaturenon-significantlyreducedatarateofabout−0.12°C/10ainstudiedareafrom1961to1989.Themeanminimumtemperatureofthecorrespondingperiodsignificantlyincreased0.20°Cevery10years.In1990–2008,themeanmaximumtemperaturesignificantlyincreasedatarateof0.9°C/10a,whilethemagnitudeofaverageminimumtemperaturerisewas0.84°C/10a.Therewereabout82%ofthestationswiththediurnalrangeshowingadowntrend,amongwhichonly50%ofthestationspassedthesignificancetest(Table4.1).ThestationswithsignificantdecreaseweremainlydistributedinYunnan–GuizhouPlateauandthesouthofHengduanMountains,whichsuggestedthatthemagnitudeof 4.1SpatialandTemporalVariationofClimateExtremes105warmingofminimumtemperatureintheseregionswasgreaterthanthemaximumtemperatureallthetime.However,thetemperatureofmoststationsinXizangPlateauandthenorthofHengduanMountainshowedanon-significantdecrease,andthetemperatureofmoststationsinSichuanBasinhadanon-significantdecreaseorincrease.Thisspatialdistributionreflectedthatthegreaterthemagnitudeoftheminimumtemperaturerose,themoreobviouslydiurnalrangereducedandviceversa(Fig.4.2).Thevariationofdiurnalrangewasaffectedbythemaximumandminimumtemperatureandwasrelatedtotheseasonalstructureofregionalwarming.Therefore,comparedwithothersindexes,thespatialandtemporalvariationshowedacertaincomplexity.AsshowninTable4.1,theannualmeanofTN90,TX90,TXx,TNxandGSLofstudiedareain1961–2008were16.1d,16.5d,31.1°C,19.4°C,and301d,respectively.AsshowninFig.4.1,thewarmnightfrequency(TN90)significantlyincreasedatarateofabout0.36d/10a,andthemagnitudeofincreasewasverysignificantafterthemidof1980s(Fig.4.1).Thereareabout95%showingauptrendamongthe110stationsselected.Thereinto,there88%ofstationshadamarkedrise,whichweremainlylocatedinothersregionsexceptfortheeasternSichuanBasin,whiletherewereseveralstationsinSichuanBasinshowingadeclinetrend(Fig.4.2).Thewarmdayfrequency(TX90)declinedslowlybeforethemidof1980sandmarkedlyroseafterward.Itsmagnitudeofchangingwas0.22d/10ain1961–2008.Therewereapproximately88%beingontherisein110stationsselected,and62%ofthestationssignificantlyincreased.Butthelowmagnitudeofchangingconfirmedthatitwasmuchgreatertowarmatnightthaninthedaytimeonceagain(Fig.4.1).Intermsofspatialdistribution,thestationswithsharpwarmingweremainlylocatedinXizangPlateau,YunnanPlateauandthesouthofHengduanMountain,whereasanumberofstationsinGuizhouPlateauandthenorthofHengduanMountainincreasedordecreasednon-significantly(Fig.4.2).Thewarmestdaytemperature(TXx)instudiedarearemarkablyincreasedatarateofabout0.11°C/10afrom1961to2008.Itincreasedslowlybeforethemidof1980sandsharplyafterward.Althoughthereare81%ofstationsbeingontheriseamong110stationsselected,only29%ofthestationspassedthesignificancetestwhicharemostlydistributedinXizangPlateau,theeasternHendguanMountain.ThemoststationsinYunnan–GuizhouPlateauandSichuanBasinhadasmallmagnitudeofincreasing,andTXxofseveralstationsreduced(Figs.4.1and4.2).Thewarmestnighttemperature(TNx)wascontinuoustoriseatarateofabout0.17°C/10a.About80%ofstationsshowedatrendofincreasein110stationsselected,and67%ofstationssignificantlywarmed.Thestationswithgreatermagnitudeofwarmingwerelocatedinthehighaltitudearea,whilethemoststa-tionsintheeasternSichuanBasinandseveralstationsinGuizhouPlateauhadadowntrend(Figs.4.1and4.2).FromtheoverallaveragelevelofSouthwesternChina,thegrowingseasonlength(GSL)increasedsignificantlyatarateof0.12d/10a,andtheinterannualchangeweresignificantlyincreasedexceptforslightdecreaseinthe1970s(Fig.4.1).TheGSLofabout96%ofstationshadarisingtrendamong110stations 1064SpatialandTemporalVariationofClimate…selected,butonly39%ofstationslocatedinXizangPlateauandHendguanMountainpassedthesignificancetest.Furthermore,themagnitudeofGSLriseinabovetwoareaswassignificantlygreaterthanotherareas.Thisspatialdistributionreflectedapparenteffectofelevation(Fig.4.2).Onthewhole,thestationswithtemperatureextremesindexsignificantlywarmingaremainlydistributedinXizangPlateauandHendguanMountain,butthestationswithnon-significantriseorreducearemainlydistributedinYunnan–-GuizhouPlateauandSichuanBasin.Thisdistributionreflectstheapparenteffectsoftheterrainandelevationandconfirmsthesignificantwarminginhighaltitudearea.ThemagnitudeoftemperatureextremesindexriseinXizangPlateauandHendguanMountainismuchgreaterthanthatinYunnan–GuizhouPlateauandSichuanBasin,whichissimilartothespatialdistributionoftheregionaltrendsofannualmeantemperature.ThestudyofLiuetal.(2009a,b)alsoconfirmedthatthemagnitudeoftemperaturerisingintheeastofQinghai–XizangPlateauanditssurroundingregionsisapparentlymorethanthatinlowaltituderegions.Inaddition,thestationwithacoolingtrendforTXn,TX90,TX10,TNx,TN90andTN10aremainlylocatedintheeasternSichuanBasin.4.1.2SpatialandTemporalVariationsofPrecipitationExtremesTheannualaveragesofPRCPTOT,SDII,RX1day,R95,R99,RX5day,CDD,CWD,R10,R20mmandR25mmare912.6mm,9.1mm/d,66.8mm,238.2mm,74mm,116.6mm,58.9d,8.4d,27.4d,10.7dand7.9d,respectivelyinSouthwesternChina(Table4.1).Comparedwithtemperatureextremesindex,thesignificanceofchangesinprecipitationextremesinsouthwestChinaislowandshowsamorecomplexspatialandtemporaldifference.Onlychangingtrendsofmaximum1-dayprecipitation(RX1day),consecutivewetdays(CWD),extremelywetdayprecipitation(R99)havepassedthesignificancetestamong11indexes.Therefore,thechangingtrendstillhasabiguncertaintyinunderstandingregionalprecipitationextremeschangeininterannualandinterdecadalscale(Table4.1).AsshowninFig.4.3,thewetdayprecipitation(PRCPTOT)in1961–2008fluctuatedtochangein10yearsperiod,butthegeneraltrendwasrisingandtheregionaltrendswas0.03mm/10a.Inaddition,thereare57%ofthe110stationsshowingaincreasingtrend(Table4.1),whichweremainlydistributedinthehighaltituderegionofXizangPlateau,HengduanMountain,YunnanPlateauandothers.However,themoststationslocatedintheGuizhouPlateauandSichuanBasinhadawidermarginofdecrease,andthestationsaccountingfor25%ofallstationswithasignificantincreasewereprimarilysituatedinXizangPlateau.Theaboveresultalsoconfirmedthattheprecipitationincreaseinthisregionmainlyhappenedinhighaltitudearea(Fig.4.4).Theannualaverageprecipitationonwetdays(SDII)hadaslowdecreasingtrendwithfluctuationsbefore1990sandincreasedafterwards. 4.1SpatialandTemporalVariationofClimateExtremes107Fig.4.3Regionalannualanomalyseries,1961–2008,forindicesofprecipitationextremesTheregionaltrendsin1961–2008was0.03mm/d/10a.Therewere59%ofstationsperforminganincreasingtrend,butonly11%ofstationshadpassedthesignifi-cancetest.MoststationhavinganincreasingSDIIliedinGuizhouPlateauandSichuanBasinandafewstationsweresituatedinXizangPlateau–HengduanMountainwherethewetdayprecipitationincreasedbyalargemargin(Figs.4.3and4.4).TherelatedresearchholdanideathatthespatialpatternofPRCPTOTdemonstratesthatitsincreaseoccurredprincipallyinhigheraltitudeareas,andthesamewastrueofSDII(Youetal.2008a,b),whichwasjustoppositetothedistributedcharacteroftheminSouthwesternChina.Thisspecialdistributedreg-ularityindicatedthattheincreaseofwetdayprecipitationinXizangPlateau–-HengduanMountainwasreallynottheresultoftheprecipitationincreaseonwetdaysbutthecontributionoftheincreasingprecipitationdaysordurationextension 1084SpatialandTemporalVariationofClimate…Fig.4.4SpatialdistributionoftrendsperdecadeforPRCPTOT,SDII,RX1day,R95,R99andR5Xday.aPRCPTOT.bSDII.cRX1day.dR95.eR99.fRX5day.gCDD.hCWD.iR10mm.jR20mm.kR25mmofprecipitationeverytime.Onthecontrary,theprecipitationintensityincreasedobviouslyinGuizhouPlateau,themostregionsofYunnanPlateauandtheeastofSichuanBasin,butthelessprecipitationleadedtosignificantdecreaseofwetdayprecipitation.ThespatialdistributionofCWDalsoprovedabovefeature.Thechangetrendofthemaximum1-dayprecipitation(RX1day)andthemaximum5-dayprecipitation(RX5day)isshowninFig.4.4,RX1daycontinuedtogrowatarateofabout0.05mm/10aduring1961–2008,anditsregionaltrendshadpassedthesignificancetest.There64%ofthe110stationsexhibitedtheincreasingtrend,butonly11%ofstationspassedthesignificancetest.Thestationswithincreasingordecreasingtrendareevenlydistributedinthestudiedarea,butthemagnitudeofincreaseofstationslocatedinthelowaltitudeareasisrelativelygreater,whichreflectsthattheextremeprecipitationeventshasbeingincreasingtosomeextent.ThefluctuationofRX5daywasquiteapparent.Ithadaweakdeclinein1961–1975,andincreasedin1976–1985.Thenitshowedafluctuatedchangeevery10years.Ingeneral,RX5daypresentedaslightincreaseandthemagnitudeis0.03mm/10a(Fig.4.3).Althoughapproximately55%ofstationshadarising 4.1SpatialandTemporalVariationofClimateExtremes109trend,only8%ofstationshadpassedthesignificancetest,whichweremainlydistributedinXizangPlateau,HengduanMountain,theeastofSichuanBasinandYunnanPlateau.Thisdistributionpartiallyreflectedtheincreaseofrainfalldaysinthehighaltitudeareas.ThestationswithadownwardtrendconcentratedonthewestofSichuanBasinandGuizhouPlateau(Fig.4.4).Theverywetdayprecipitation(R95)rosebefore2000inthestudiedarea,andshowedafallingtrend.Onthewhole,R95increasedattherateof0.04mm/d/10abutfailedtopassthesignificancetest(Fig.4.3).Approximately63%ofthestationswereontherisebutonly10%ofthestationspassedthesignificancetest,whichweremainlydistributedinXizangPlateau,thesouthofHengduanMountain,YunnanPlateau,GuizhouPlateauandtheeastofSichuanBasin.WhilethestationswithadecreasetrendwereprimarilylocatedinthenorthofHengduanMountainandthewestofSichuanBasin(Fig.4.4).Thevariationofextremelywetdayprecipitation(R99)wassimilartotheverywetdayprecipitation(R95),butitsincreasingtrendismoreapparent.Overall,R99increasedattherateof0.05mm/d/10aandpassedthesignificancetest,whichindicatedthepossibilityofprecipitationextremeseventshadbeenincreasingyearbyyear(Fig.4.3).IntermsofR99,althoughtherewere67%ofthestationssituatedinlowaltitudeareasandshowinganincreasingtrend,only8%ofstationshadpassthesignificancetest.Aboveanalysisdemonstratedthatthesignificancelevelofchangetendencyinextremeprecipitationindexwasrelativelylowinthestudiedarea.Butwhatneedtobeemphasizedisthattheprecipitationincreaseinthehighaltitudeareachieflyisaresultoftheincreasingprecipitationdaysordurationextensionofprecipitationeverytime.Thenumbersofprecipitationandtherainydayshadaremarkableincreasingtrendinthehighareasandtherainfallintensityincreasedobviouslyinthelowaltitude.Theconsecutivedrydays(CDD)instudiedareahadafluctuateddeclinechangeinotherperiodsinsteadofarisingtrendin1990s.Onthewhole,CDDdecreasedatarateofabout0.05d/10a(Fig.4.3).Therewere74%ofstationsinthestudiedareasbeingonthedecline,butonly28%ofstationspassedthesignificancetest.ThestationswiththesignificantfallingtrendaremainlylocatedinXizangPlateau,whichprovedtheincreaseofrainydays.However,thestationsshowingarisingtrendaremainlydistributedinYunnanPlateauandSichuanBasin,whichreflectedthedecreaseofrainydays(Fig.4.4).Theconsecutivewetdays(CWD)inSouth-westernChinahadasharpdeclinein1961–1961followedbyaslightincrease.After2000,itbegantodrasticallyreduceagain.Generally,CWDshowedadecreasingtrendatarateof0.08d/10aandhadpassedthesignificancetest(Fig.4.3).CWDofabout76%ofthestationslocatedinGuizhouPlateauandSichuanBasinreducedinthestudiedarea.Thereinto,19%ofallstationsituatedinSichuanBasinhadaremarkabledecline.Furthermore,anumberofstationinHengduanMountaindecreasedapparently.However,thestationswithaincreasingtrendweremainlydistributedinXizangPlateauandthecentralofHengduanMountain.Thisspatialdistributionpatternconfirmedagainthattheprecipitation 1104SpatialandTemporalVariationofClimate…increaseinthehighaltitudeareawastheresultoftheincreaseofrainydays.Buttheprecipitationincreaseinthelowaltitudeareawasmainlycausedbythedecreaseofrainydaysandtheincreaseofrainfallintensity(Fig.4.4).Generally,CDDandCWDshouldhadtwoapproximatereversechanges,andonlyXizangPlateauandthecentralofHengduanMountainshowedtheapparentoppositetrendinSouth-westernChina.CDDandCWDinotherregionsexhibitedacommondecrease,whichmayberesultedintheseasonalstructureofrainyday.FromtheanalysisofChap.3,itcouldbefoundthattheprecipitationincreaseinwintermonsoonperiodwasquiteapparent,whichsuggestedthattheincreaseofrainydaysmaybeareasonofthedecreaseofCDD.WhilethereductionofCWDmainlyistheresultofthedecreaseofrainydaysinsummermonsoonperiod.Thenumberofheavy(R10mm),heavier(R20mm)andheaviestprecipitationdays(R25mm)hadaweakincreasingtrendwithfluctuations(Fig.4.3).Morethanhalfofthestationsexperiencedanincrease,butitwassignificantataminority(Table4.1).Spatially,XizangPlateauandHengduanMountainsstationsdisplayedincreasingtrendsforR10mm(heavyprecipitationdays),andmostofthemhadpassedthesignificancetest.Accordingthispoint,itwasconfirmedthatprecipita-tionincreaseofthehighaltitudeareawastheresultoftheincreaseofrainydays.ThestationshavingadecreaseweredistributedinSichuanBasinandthecentralandeastofYunnan–GuizhouPlateau,andsomestationdeclinedsignificantly(Fig.4.4).ForR20mmandR25mm,anumberofstationsinXizangPlateau,Yunnan–GuizhouPlateauandSichuanBasindisplayedincreasingtrends,whereastherewasalotofstationsexhibitingdecreasetrendinthenorthofHengduanMountainandGuizhouPlateau,andSichuanBasin(Fig.4.4).Theseresultsindi-catedthattheincreaseofrainydays,especiallyR10mm,isamainfactorresultingintheprecipitationincreaseinXizangPlateauandHengduanMountain.R20mmandR25mmalsopresentedaremarkableincrease.SouthwesternChinaislocatedinthetransitionzonebetweenthefirstladderandthesecondladderandisthesourceregionofnumerousrivers.Thelandslideanddebrisflowalsohappenmostfrequentlyinthisregion.Itisinevitablethattheincreaseofrainydayswillmakethepossibilityoftheoutbreakofvariousgeologicaldisastersintensified,soithasanimportantpracticalsignificancetostrengthenthemonitoring,forecastandpre-ventionresearchofmeteorologicaldisasters.Onthewhole,thespatialandtemporalvariationsofPRCPTOT,R10mm,R20mmandR25mmindicatethattheincreaseofrainydaysinhighaltitudeareaisquiteoutstandinganditisanimportantcontributioncausingtheprecipitationincrease.ThevariationsofRX1day,R95,R99,RX5dayandsomesuggestthatalthoughextremeprecipitationeventsinthestudiedareahasincreasedinrecentyears,thetrendstillfailedtopassthesignificancetest.ThechangesofCDD,SDIIandCWDandothersdemonstratethattheprimarycharacterofextremeprecipi-tationchangeinSouthwesternChinaisthattherainydaysathighaltitudeandtherainfallintensityatlowaltitudeincreaseapparently,buttheirchangingprocessandmechanismstillneedtoverifybydatarecordedinlongperiod. 4.2ComparisonAmongClimateExtremesIndexes1114.2ComparisonAmongClimateExtremesIndexes4.2.1TheConsistencyofClimateExtremesIndexesAsshowninTable4.2,thefirstfactorincludedalmostalltemperatureextremesindexesexceptforDTRintheresultsoffactoranalysis,accountedfor52%oftheoverallvarianceofthetemperaturedata,andindicatedtheconsistentandcommonwarmingtrendoftemperatureextremesindex.Theabovecontentcouldbeprovenbythesignificantcorrelationbetweenindexes(Table4.3).DTR,whichreflectstherelationshipbetweenmaximumandminimumtemperatures,dominatedthesecondfactorandaccountedfor14%oftheoverallvarianceofthetemperaturedata.Withthemoreobviouswarmingofmaximumprecipitationinrecentyears,thechangeofDTRhadshiftedfromtheleadingfactorofthemaximumtemperaturewarmingtothecommoneffectofbothmaximumandminimumtemperature.Therefore,thedifferencebetweenthemdecreasedwiththeincreaseofthemagnitudeofmaximumtemperaturerise(Fig.4.1).TNxandIDdominatedthethirdfactorandaccountedfor7%oftheoverallvarianceofthetemperaturedata,indicatingthedeclineofIDwasinrelationtotheriseofTNx.GSLdominatedthefourthfactorandaccountedfor7%oftheoverallvarianceofthetemperaturedata.Itwasmainlyaffectedbythechangeofcoldesttemperature.TherelevancewithID,TN10,TNnandTX90alsoconfirmedtheriseofminimumtemperaturewasthemainreasonoftheincreaseofgrowthdays.Theresultsoffactoranalysis(Table4.2)showsthatallindexesdominatedthefirstfactorandaccountedfor59%oftheoverallvarianceofthetemperaturedata,reflectingtheconsistencyoftheannualtotalprecipitationandthechangingtrendofprecipitationextremesandindicatingthatthecontributionrateofprecipitationextremestoannualprecipitationincreasesgradually(Table4.4).Inaddition,italsoconfirmsthenon-significanceoftheprecipitationchangetrendinSouthwesternChina.R99andRX1daydominatesthesecondfactorandaccountsfor59%oftheoverallvarianceofthetemperaturedata,indicatingthatRX1dayistheprimaryinfluencingfactorofR99.Thethirdfactorsaccountsfor9%oftheoverallvarianceofthetemperaturedataandisdominatedbyCDD.CDDhasarelativitywithotherindexes.Althoughitshowsadecreasingtrend,itpresentsasignificantlyregionaldifference.Anditschangeismainlydecidedbytheseasonalstructureofrainydays.CWDdominatesthefourthfactorandaccountsfor8%oftheoverallvarianceofthetemperaturedata,becauseitschangeismainlyaffectedbythevariationofrainydaysinsummermonsoonperiod.CDDandCWDarecharacterizedbydecliningtrendbutfordifferentcauses,whichreflectsthecomplexityandparticularityofregionalprecipitationchange.Thisalsocanbeshownintheweakcorrelationwithotherprecipitationindexes(Table4.4).ThereareremarkablecorrelationsamongPRCPTOT,R10mm,R20mm,R25mm,R95,R99,betweenRX1dayandRX5day.Ontheonehand,itisbecausetheextremeprecipitationeventsmainlyoccurredinsummermonsoonperiod.Ontheotherhand,italsoreflectstheincreasingtrendofextremeprecipitationinthestudiedarea(Table4.4). 1124SpatialandTemporalVariationofClimate…0.130.130.160.050.060.38−−−−−−0.060.210.080.040.210.070.170.140.010.01−−−−−−−0.090.030.850.080.280.230.160.30.080.120.120.12−−−−−−0.330.010.480.320.570.290.10.120.30.262345−−−−−−0.10.510.730.320.29Factors1−0.110.910.740.870.90.90.760.280.790.510.820.480.750.270.320.32Precipitation0.04CDD0.03Prcptot0.25R200.070.13RX1dayRX5day−−−−−0.010.020.310.08R100.190.180.090.25Rnn0.27R950.35R990.170.45SDII−−−−−−−0.430.20.350.640.020.290.31Annualprecipitation0.2CWD0.890.040.56−−−−−−0.390.010.590.010.30.320.170.390.02−−−−−−2012a).Copyright(2012),withpermissionfromElsevier0.880.360.670.080.810.30.79Factors12345Index0.04−0.860.44−−0.850.840.69−0.120.820.690.560.40.660.390.070.320.27ResultsoffactorloadingsperceptualexplainedvarianceintemperatureandprecipitationextremesTable4.2TemperatureIndexDTRFDGSLIDTN10TN90TNnTNxTX10TX90TXnTXxPercentageofvarianceReprintedfromTheLancet:Lietal.(5214137 4.2ComparisonAmongClimateExtremesIndexes1131.001.000.281.000.750.500.600.440.601.00−−−0.501.00−0.200.461.00−0.691.00−0.810.660.580.600.700.550.410.840.410.480.400.480.550.690.450.600.751.00−−−−−−0.350.650.240.440.840.301.00−−−0.46−−0.67−0.330.310.360.191.00−−0.290.04−0.270.07cientsoftemperatureextremesfi0.550.700.870.510.510.550.620.310.44−0.62−−−−−−cantatthe5%levelaresetinboldfi0.050.210.090.120.130.350.56DTRFD−−GSL0.34−ID−0.78−−TN100.40TN90TNnTNxTX10TX90TXnTXxThecorrelationcoefTable4.3DTRFDGSL1.00ID0.21TN10TN901.00TNnTNxTX10TX90TXnTXxValuesfortrendssigni0.160.17 1144SpatialandTemporalVariationofClimate…1.001.001.00RX51.001.001.00RX11.001.000.890.850.830.790.740.700.550.450.590.930.260.630.680.340.490.410.410.780.460.410.510.560.560.660.840.630.810.720.820.930.730.790.600.820.020.010.070.06−−−−0.090.241.000.260.170.070.290.040.170.021.000.050.110.09cientsofprecipitationextremesfiPrcpCDDCWD−tot−−−R10−−R200.060.05R25−0.19r95pr99DayDaySDIIcantatthe5%levelaresetinboldfi0.211.00−0.180.950.870.840.800.710.510.560.630.51ThecorrelationcoefTable4.4TotalprecipitationPrecipitationCDD1.00CWDPrcptotR10R20R25R95R99RX1dayRX5daySDIIValuesfortrendssigni 4.2ComparisonAmongClimateExtremesIndexes115Fig.4.5Regionalseriesforatheratiooftheindexofprecipitationonverywetdays(R95)tototalprecipitationandbtheratiooftheindexofprecipitationonextremelywetdays(R99)tototalprecipitationAsshowninFig.4.5,in1961–2008,theaveragecontributionrateofverywetdayprecipitation(R95)toannualprecipitation(0.38%/10a)inSouthwesternChinais26%.Theminimumis22%,andthemaximumis32%happeningin1998.Onthewhole,theratioofR95inannualprecipitationcontinuestorise.Thecontri-butionrateofextremelywetdayprecipitation(R99)toannualprecipitationincreasesatarateof0.31%/10aandpassesthesignificancetest.Theaveragecontributionratewas8.2%in1961–2008,andtheminimumandmaximumwere5.7and11.7%,respectively.ThetotalcontributionrateofR95andR99toannualprecipitationwas34.2%.Theincreasingtrendofcontributionratesuggestedthattheextremeprecipitationeventsincreasedyearbyyearinthestudiedarea.Therelatedresearchesalsoconfirmedthat95%ofthenetprecipitationincreaseismainlyfromR95(Youetal.2010a,b,c,d).Intermsofregionaldifferences,theratioofR95intheannualtotalprecipitationofXizangPlateau–HengduanMoun-tain,Yunnan–GuizhouPlateauandSichuanBasinwere18,26and31%,respec-tively.TheratioofR99were5,8and10%.Obviously,R95ofSichuanBasinmakemostcontributiontotheannualtotalprecipitation,whichreflectsthesig-nificantincreaseofextremeprecipitationeventsinthelowaltitudearea.4.2.2TheRegionalDifferenceofClimateExtremesIndexesAsshowninTable4.5,theaveragesofTX10,TN10,TN90andTX90inXizangPlateau–HengduanMountain,Yunnan–GuizhouPlateauandSichuanBasinweresameformanyyears.Fromotherindexes,itcouldbeshownthattheaverageofXizangPlateau–HengduanMountainwasmaximum,SichuanBasinfollowedandYunnan–GuizhouPlateauislastone.Thetemperatureextremeindexesofthreesub-regionsin1961–2008showedaclearwarmingtrend.ThetemperatureextremeofXizangPlateau–HengduanMountaincontinuedtowarm,andthewarming 1164SpatialandTemporalVariationofClimate…Table4.5Trendperdecadeforregionalindicesoftemperatureandprecipitationextremesinthreesub-regions(°Cormmord/10a)IndexXPHMSBYGPAverageRegionalAverageRegionalAverageRegionaltrendstrendstrendsTX1016.5−0.2316.5−0.0916.5−0.08TN1016.3−0.4416.4−0.3316.3−0.35TXn−2.10.122.60.1250.15TNn−17.20.3−3.50.24−1.50.33ID21.1−0.154.5−0.091.2−0.04FD165−0.3419.8−0.2811.4−0.26DTR13.9−0.267.60.019.5−0.29TN9016.20.4515.60.2516.30.36TX9016.50.2816.50.2216.50.15TXx26.30.1635.30.1233.80.05TNx130.2725.20.0622.90.18GSL229.40.243400.2353.10.11PRCPTOT583.50.21,109.8−0.091,143.1−0.02SDII6.9010.60.0210.60.06RX1day34.90.07104.70.0479.80.05R951200.08358.9−0.012960.04R9933.50.09117.40.04930.05RX5day73.00.05166.40.06135.40.006CDD92.7−0.1231.6038.9−0.05CWD8.90.0187.1−0.158.7−0.1R10mm18.50.1329.2−0.1335.4−0.06R20mm3.20.0814.3−0.0916.30.01R25mm2.90.0810.5−0.0611.80.05Valuesfortrendssignificantatthe5%levelaresetinboldmagnitudewassignificantlygreaterthantheothertwoareas.Theregionaltrendsof12indexeshereallpassedthesignificanceleveltest,whilethere8and6indexesrespectivelyinYunnan–GuizhouPlateauandSichuanBasinpassedthesignificanceleveltest.Intermsoftheabsolutevalueofregionaltrends,Yunnan–GuizhouPlateauwasslightlygreaterthanSichuanBasin.Whatthemostapparentinteran-nualvariationisthattheextremetemperatureindexhadaslowriseorweakdeclinebeforethemidof1980sandsharplywarmedafterward.Inaddition,generallythreesub-regionswerecharacterizedbythatthewarmingrangeofcoldnessindexesandnightindexesweregreaterthanthatofwarmthindexesanddaytimeindexes.Thedifferenceoftemperatureextremesindexesbetweenregionsfurtherconfirmedthatawidermarginofwarmingoccuredinthehighaltitudearea.In1961–2008,themaximumaverageofPRCPTOT,SDII,CWD,R10mm,R20mmandR25mmwasinYunnan–GuizhouPlateau,SichuanBasinfollowed 4.2ComparisonAmongClimateExtremesIndexes117andtheaverageoftheminXizangPlateau–HengduanMountainisminimum,whichwasconsistentwiththedifferenceofannualtotalprecipitation.RX1day,RX5day,R95andR99isgreatestinSichuanBasin,followedbyYunnan–GuizhouPlateau.ThemaximumCDDoccurredinXizangPlateau–HengduanMountainandYunnan–GuizhouPlateaufollowed.Itshowedagainthattheprecipitationextremeseventsmainlyinlowaltitudeareaoverthepassed50years,especiallyinSichuanBasin(Table4.5).TheprecipitationextremesindexinXizangPlateau–HengduanMountainappearedanobviousincreasingtrend.ExceptingthechangingtrendofRX5day,SDIIandCWDcouldnotpassthesignificancetestandtheCDDwassignificantlyreduced,otherprecipitationindexweresignificantlyincreased.ThesignificantincreaseofPRCPTOTalsoconfirmstheincreaseofrainfallinthearea,thesignificantincreaseofotherprecipitationindexesshowedthattheincreaseofrainydayswasamainfactorresultingintheincreaseofregionalprecipitation.However,thenon-significantchangeofRX5day,SDIIandCWDverifiedthattheextremeprecipitationeventsandprecipitationintensityincreasednon-significantly.ThesignificantreductionofR10mm,R20mmandCWDinSichuanBasinrevealedthattheapparentfeatureofextremeprecipitationvariationandthemainreasonoftotalprecipitationdecreaseinrecentyearswasthereductionofrainydayswhichwillcertainlyleadtotheunevendistributionofrainytimeandtheincreaseofextremeprecipitationevents.TheregionaltrendsofRX1day,R99andCWDinYunnan-GuizhouPlateauhadsucceededinthesignificancetest,whichrevealedthattheincreaseofextremeprecipitationeventsandtherainfallintensitywasapparentinthisregionwasapparent,andindicatedagainthattheincreaseofextremeprecipitationinthestudiedareawasmainlyoccurredinlowaltitudearea.SDIIidentifyingrainfallintensitykeptastablestateinXizangPleteau–HengduanMountain,andshowedaincreasingtrendinYunnan–GuizhouPlateauandSichuanBasin.Furthermore,CWDsignificantlyreducedinlattertworegion,whichaffirmedprecipitationintensityincreasedinlowaltitudeareawhilerainydaysreduced.Allinall,theregionaldifferenceofextremeprecipitationcanbemadeaconclusionthatthewarmingmagnitudeathighaltitudeareaisgreaterthanthatoflowaltitudearea;thesignificantincreaseappearedinrainydaysathighaltitudeareas,andtherainydaysreducedinlowaltitudebutprecipitationintensityincreased;althoughtheextremeprecipitationeventsshowedanincreasingtrend,butthistrendjustissignificantinlowelevationarea.4.2.3TheComparisonofColdnessandWarmthIndexesInordertogetmoreknowledgeofchangingindailymaximumtemperatureanddailyminimumtemperature,acomparisonaboutthetendencyoftheextremecoldnessandwarmthindexhadbeenmadeinTable4.6.Intermsofwarmdayfrequency(TX90)andcolddayfrequency(TX10),theregionaltrendsofTX90inabout83%ofthestationswas1.64timesgreaterthanthatofTX10.Theregional 1184SpatialandTemporalVariationofClimate…Table4.6NumberandComparisonBasisQualifiedpercentageofstationsproportionofindividualTX90>TX10abs83stationswherethetrendinoneindexisofgreaterTN90>TN10abs48magnitudethanthetrendinaTXx>TXnrel31secondTNx>TNnrel12TXx>TNxrel42TXn>TNnrel18TX90>TN90abs21TX90>TN10abs24TX10>TN10abs5TN90>TX10abs95ID>FDabs5absabsolutevalue,relrealvaluetrendsofwarmnightfrequency(TN90)inabout48%ofthestationswaswiderthanthatofcoldnightfrequency(TN10),buttheabsolutevalueoflatteronewasmorethanthatofformerone.Theregionaltrendsofcoldestdaytemperature(TXn)was0.021°Cmorethanthatofwarmestdaytemperature(TXx),andtheformerindexwasgreaterthanlatterindexinabout69%ofstations.Theregionaltrendsofcoldestnighttemperature(TNn)was2.23timesmorethanthatofcoldestdaytemperature(TXn),andtheformerindexwasgreaterthanlatterindexinabout82%ofstations.Therewereabout58%ofthestationswheretheregionaltrendsofTXxwasgreaterthanthatofTXn.Therewere82%ofstationswheretheregionaltrendsofTNnwasgreaterthanthatofTXn.TheregionaltrendsofTN90was1.65timesgreaterthanthatofTX90whichexistingin79%ofstations.TheregionaltrendsofTNnwas2.85timesofTNx.Aboveanalysisindicatesthatthewarmingmagnitudeofcoldnessindexes(TN10,TXn,TNN)aresignificantlygreaterthanpartofwarmthindexes(TN90,TXx,TNx).IPCC(2007)thinksthatthemainreasonisthemorewarmingmag-nitudeofwinterthansummer.Itsphysicalmechanismisthewatervaporcontentinwinterislessthaninsummer,sotheradiationforceofgreenhousegasesstrengthensinwinterthuscausingthemuchwidermarginofwarming(Aguilaretal.2009).Thewarmingmagnitudeofnightindexes(TNx,TNn,TN10,TN90)issignificantlygreaterthandaytimeindexes(TXx,TXn,TX90,TX10).Themoreobviousthingisthatthestationswithawarmingtrendinnightindexesaredistributedevenly.ButonlyTX90andTX10indaytimeindexesshowsimilarcharacteristics,therestindexesjustincreaseremarkablyinhighaltitudearea.Numerousstudieshaveconfirmedthewarmingtrendofextrememinimumtemperatureisgreaterthanextrememaximumtemperature,andthenightindexeswarmmoresharplythandaytimeindex(Easterlingetal.2000;Mantonetal.2001;Griffithsetal.2005;KleinTanketal.2006;Vincentetal.2005). 4.2ComparisonAmongClimateExtremesIndexes1194.2.4TheComparisonofThisStudyandOtherSourcesAlthoughtheclimateextremesindexinSouthwesternChinahasasametrendtootherregionsintheworld,theretheapparentdifferencecanbeshown.AsshowninTable4.7,theresearchdurationsalmostareinthelatter50yearsof20thcentury.ItisfoundthattheregionaltrendsoftemperatureinthestudiedareaissignificantlylowerthanthatofotherareasprobablycausedbythedifferentcalculationmethodsindifferentareasorindicatingthelesswarmingmagnitudeinSouthwesternChina.Before,“ClimateandEnvironmentalEvolutioninChina”(Qinetal.2005)reportedthatthemagnitudeoftemperaturechanginginthisregionisleastinChinaandthetemperatureofsomeregionsshowedadecreasetrend.Themostapparentthingisthatthewarmingmagnitudesofwarmestandcoldestdaytemperatureaswellaswarmestandcoldestnighttemperaturearemuchlessthanthatofotherregionsintheworld.AndthechangingrateoficedaysinSouthwesternChinaisleastandnon-significant,butthedecreasingmagnitudeofdiurnaltemperaturerangeismuchmorethanthatofotherregionsintheworld(excludingthecentralandeastofQinghai-XizangPleteau).ThestudyofYouetal.(2010a,b,c,d)onextremetemperaturesinChinaindicatesthatthedecreasingmagnitudesofNortheasternChina,NorthernChinaandNorthwesternChinaareremarkablymorethantheSouthernChina,whichiscausedbythewiderwarmingmagnitudeofminimumtemperatureinNorthernChina(ZhaiandPan2003).Inaddition,anumberofstudiesalsothinkthattheurbanheatislandeffectisamaincontributiontothewidermarginofdecreaseofdiurnaltemperaturerange(Griffithsetal.2005;Jonesetal.2008;Renetal.2008).Themeaningofcomparisonisnotveryimportantduetothecomplexityandregionaldifferenceofprecipitationindexvariationaswellasthesignificanceoflessmagnitudeofextremeprecipitationindexinthestudiedarea.However,themostapparentthingisthatthemagnitudeofextremeprecipitationindexisverysmallinthestudiedarea.Tosumup,formajorregionsintheworld,theclimateextremesindexeshaveaslightchange.4.3DrivingMechanismforClimateExtremes4.3.1TheCorrelationwithClimateExtremesandAtmosphericCirculationThesignificantcorrelationwithtemperaturechangeandsealevelpressureinSouthwesternChinacanbefoundfromtheanalysisoflastchapter.Inordertofurtherstudytheroleofcirculationvariationinthechangeofclimateextremesdiscussedabove,thisstudydrawsthecirculationcompositefiguresat500and300hpainspring,summer,autumnandwinterbetween1961–1985and1986–2008bymeansofNCEP/NCARreanalysisdata,andselects0°–70°Nand30°–170°Easthestudiedareathrough1986–2008minus1961–1985togetthecirculationdifferenceofboth. 1204SpatialandTemporalVariationofClimate…2006)––1.711.2231.130.8712.191.540.06WesterncentralAfrica−−0.130.2302.873.240.250.21−0.06−−−−Aguilaretal.etal.2003)(1955–)2.42.20.30.30.12.51.70.30.28.70.32.63.50.4CentralandnorthernsouthAmerica−−18.1Aguilar(20052000)(1961–)1.6310.180.270.012.242.350.160.190.050.080.050.020.333.57SouthernandwestAfrica−−−Newetal.(2006)2000)(19612006–°Cormmord/10a)southernAsia5.7−2.60.730.124.726.860.176.871.026.461.26−−KleinTanketal.()b2003)(1961,–1.30.40.60.120.30.0060.35−−0.20.28−−0.661.20.070.23−−0−0−Zhangetal.(2005a)2003)(19502006–1.260.620.080.55−−0.37−0.890.2110.590.850.55−Alexanderetal.(2005)(1951)–2.060.470.350.633.730.180.710.621.750.070.213.041.583.210.060.31.374.060.051.91.224.07ChinaGlobal−−MiddleeastCentraland−−−(2010a)Youetal.2008a).Copyright(2012)withpermissionfromElsevier2005)2.380.85(19610.30.692.464.320.21.261.580.280.254.256.660.030.271.281.090.084.640.070.23–−−−−−−−−2012aEasternandcen-tralTibetanPlateau0.370.130.130.290.090.290.180.220.360.110.170.120.030.030.050.040.050.030.050.080.000.000.022008)−(1961−−−−−−cantatthe5%levelaresetinbold–fiternChina(1961ThisstudyYouetal.(Trendsoftemperatureandprecipitationextremesfromthisstudyandothersources(Table4.7IndexSouthwes-TN10TX10TXnTNnIDFDDTRTX90TN90TXxTNxGSLPRCPTOTSDIIRX1dayR95R99RX5dayCDDCWDR10mmR20mmR25mmDatasourcesReprintedfromTheLancet:Lietal.(Valuesfortrendssigni 4.3DrivingMechanismforClimateExtremes121Table4.8Trendperdecadeforregionalindicesoftemperatureandprecipitationextremesbetween1961–1985and1986–2008(°Cormmord/10a)TemperatureRegionalRegionalPrecipitationRegionalRegionalindextrendtrendindextrendtrendTX100.2−0.49PRCPTOT0.080.07TN10−0.2−0.53SDII−0.010.16TXn−0.150.09RX1day0.080.02TNn0.150.22R950.080.01ID0.160.06R990.08−0.01FD−0.08−0.21RX5day0.070.003DTR−0.390.09CDD−0.030.01TN900.090.74CWD−0.19−0.11TX90−0.20.73R10mm0.030.09TXx−0.110.19R20mm0.050.08TNx0.070.25R25mm0.060.08GSL−0.060.04Valuesfortrendssignificantatthe5%levelaresetinboldThemainreasonsofselecting1985astheseparationareasfollows:(1)AsshowninTable4.8,thewarmingmagnitudesofalltheextremetemperatureindexin1986–1986aregreaterthanin1961–1985;TX10,TXn,TX90,TXxandGSLshowthecoolingtrends,butwarmsignificantlyin1986–2008;thereareeightindexchangesin1986–2008passingthesignificanceleveltestinsteadofthreeindexesin1961–1985.(2)Intermsofprecipitationindexes,therearefiveindexchangespassingthesignificancetestin1961–1985butonlytwoindexesin1986–2008;From1961–1985to1985–2008,theincreasingmagnitudeofPRCPTOT,RX1day,RX5day,R95,R99,R10mm,R20mmandR25mmdeclinedsignificantly,andthemagnitudeofSDIIandCDDturnedincreasefromdecrease.AsshowninFig.4.6,themaximumdifferenceofgeopotentialheightat500hpainsummerbetween1961–1985and1985–2008occurredinsurrounding45°Nand100°E.Theformerperiodisnearly40gpmhigherthanthelatterone.ItconfirmsthatthepowerfulanticyclonecirculationdevelopsinEurasiaandthecenterislocatedinMongoliaandLakeBaikal.Inaddition,thereisacycloniccirculationdevelopinginthewestPacificOceannearJapananditscenteris35°Nand155°E.Underthecontrolofhighpressuresystem,mostareasinChinaareaffectedbythedryandwarmair,andthestudiedareaalsoiscontrolledbydryandhotnortherlywinds.Butthenortherlywindshindersthenorthwardmovingofseawarmaircurrentandcausesthewarmanddrycirculation,whichwillcausetheapparenttemperaturerise.AbovecirculationbackgroundsuggeststhattheAsianmonsoonsystemstrengthweakenedin1986–2008andcausedtheprecipitationdecreaseinthestudiedarea,comparedwith1961–1985.Thiskindofcirculationpatternissimilarto300hpaisobaricsurface(Fig.4.7).Therefore,thenortherlywindsinSouthwesternChinablocksthenorthwardmovingoftheoceanswarmaircurrent,leadstothesharpriseoftemperaturesin 1224SpatialandTemporalVariationofClimate…Fig.4.6Differenceofwindspeedandgeopotentialheightat500hPainsummer(a),autumn(b),winter(c)andspring(d)between1986–2008and1961–1985.ReprintedfromtheLancet:Lietal.(2012a).Copyright(2012),withpermissionfromElseviersummerandcausesthedecreasingfrequencyofprecipitation.ThestudyofZhangetal.(2008a,b,c)alsoconfirmedthatthestrengtheningofgeopotentialheightinMongoliainsummeristhekeyreasonoftherapidwarminginChina,andthecirculationfielddevelopedbecauseofabovereasonwillbeinclinedtoblockthenorthwardmovingofanyoceansaircurrent.AnanticyclonesystemisdevelopedinEurasiainautumnandcenteredasWesternMongoliaandNorthwesternChina,whichissimilartosummer.Buttheinfluencedrangeofanticyclonecenterinautumnismuchwiderthaninsummer,evenSouthwesternChinaiswithinthescopeofthedirecteffect(Figs.4.6and4.7).Underthebackgroundofthiscircu-lation,thestudiedareaiscontrolledbyhotanddryairmassandnortherlywindsprevailshere.ThecirculationpatternsalsoconfirmsthattheweakeningoftheAsianmonsoonsystem.Thestrengtheningnortherlywindsblockstheoceanairmassresultingintheinfluenceofhotanddryaironthestudiedarea,whichwillleadtothesignificantincreaseofscorchingweatherandthedecreaseofrainfall.InwinterofEurasian,ananticyclonesystemdevelopsinMongoliaandLakeBaikalregion,atthesametime,aabnormalcyclonesystemformin500°Nand50°E.Theirdifference(−25gpm)ingeopotentialheightofcentersalsoshowsaboveconclu-sion.Thiscirculationpatternreflectstheincreaseofintensityofwesterlywinds 4.3DrivingMechanismforClimateExtremes123Fig.4.7Differenceofwindspeedandgeopotentialheightat300hPainsummer(a),autumn(b),winter(c)andspring(d)between1986–2008and1961–1985.ReprintedfromTheLancet:Lietal.(2012a).Copyright(2012),withpermissionfromElsevierfrom1961–1985to1986–2008(Figs.4.6and4.7).Underthebackgroundofthis,thesouthwestwindprevailinNorthwesternChinaandthenorthofit,andSouth-westernChinaismainlycontrolledbythesouthwestlywarmandwetairmass.Thiswindfieldstructurewillweakenthestrengthofthewintermonsoon,whatisworse,itwillreducetheinvadingtowardsouthofwintermonsoonandcoldair.Inaddition,thispatternwillleadtoadropinextremecoldeventsinwinterandtemperaturesrise,whichpartlyexplainsthesignificantwarminginwinter.Inthespring,asamecirculationpatterntowinterisshown,butitsintensityandinfluencedscopeofanticycloneandcyclonesignificantlyreduce,comparedwithwinter.Itindicatesthatthestrengtheningofwestwindandtheformationoftheeastandsoutheastwindinwintermonsooncreatesagoodcirculationbackground.Figure4.8demonstratesthedifferenceofannualmeanwatervaporflux(a,b)andlongitudinalwindspeed(c,d)between1986–2008and1961–1985.ThemostobviousinformationinthisfigureisthatthewatervaporfluxofthemajorregionsinSouthwesternChinakeptstableexceptthatofeasternXizangPlateauandthenorthernHengduanMountainhadaslightincreasefromformerperiodtolatterperiod.Moreimportantly,thelongitudinalwindspeedoftwoisobaricsurfacesexhibitedapparentdeclinetrend(Fig.4.8).Thesetwocharacteristicsreflectthe 1244SpatialandTemporalVariationofClimate…Fig.4.8Differenceofannualmeanwatervaporflux(a,b)andlongitudinalwindspeed(c,d)between1986–2008and1961–1985(aandcisat500hPa;banddisat300hPa).ReprintedfromtheLancet:Lietal.(2012a).Copyright(2012),withpermissionfromElsevierweakeningofmonsooncirculationandwatervaportransportinrecentyears.AccordingtoAsianmonsoonindexcalculatedbyGuoetal.(2003),itwasfoundthattheeastAsianmonsoonhaddrasticallyreducedsince1961,southAsianmonsoonalsohadafluctuatedchangecharacterizedbystrengthreducing,(Fig.4.9)whichprovedthattheweakeningoftheAsianmonsoonsystemonceagain.Wang(2001)thoughtthattheweakenedmonsooncirculationsystemsincethe1970sbroughtmoreprecipitationforSouthernChinabutweakenedthewatervaportransporttowardnorth.ThestudiesofDashetal.(2008)andWu(2005)alsoconfirmedthatIndianmonsoonsystemreducedinnearlydecadesandbecamemoreandmoreunstable.TheresearchesofDingetal.(2005),GongandWang(2000)andXuetal.(2006a,b)alsoholdtheideathattheweakenedAsianmonsoonsystemresultedinmoreextremeprecipitationeventsinChinaandtriggeredfloodsinthesouthofChina.TheweakeningofthemonsooncirculationandwatervaportransporthadproducedimportantinfluencesonthechangeofextremeprecipitationinSouthwesternChina,butitsimpactmechanismstillneedsmorefollow-upstudiestoidentify. 4.3DrivingMechanismforClimateExtremes125Fig.4.9ChangeofEasternAsiamonsoonindexandSouthernAsiamonsoonindexduring1961–20014.3.2TheCorrelationwithClimateExtremesandElevationAgoodstatisticalrelationshipbetweenextremetemperatureindexandelevationinSouthwesternChinaexisted.ThecorrelationcoefficientofDTR,FD,ID,TN10andTX10andelevationhadpassthesignificancetestof0.05,andthevalue(P)ofFD,ID,TN10andTX10lessthan0.0001,thatisP<0.0001.Thefiveindexesshowingdecreasingtrendallhadanegativecorrelationwithelevation,whichreflecttheregionaltrendincreasedwiththeriseofelevation.ThewarmingmagnitudeofGSL,TN90,TNnandTNxshowedaincreasingtrendalongwiththeriseofelevation,butthemagnitudeofTXn,TX90andTXxhadnotpassedthesignificancetest.Allinall,thewarmingmagnitudeofthestudiedareain1961–2008becamegreaterwiththeriseofelevation.Intermsoftheobviousdegreeofelevation,thecoldnessindexes(TN10,TX10andTNn)isgreaterthanthewarmthindexes(TN90,TX90andTNx)andnightindex(TNn,TNx,TN10andTN90)isgreaterthanthedaytimeindex(TXn,TXx,TX90andTX10).Inaddition,onlythestatisticalrelationshipofTX10withthealtitudepassedthesignificancetest.AsshowninTable4.9,intermsoffiveindexesperformingdeclinetrend,themaximumwarmingmagnitudeofID,TX10,TN10andDTRoccurredin4,500–5,000mofelevation,andonlythatofFDappearedin2,000–2,500mofelevation,reflectingthesignificantwarmingofhighaltitudeareas.ThemaximumwarmingmagnitudeofGSL,TN90andTNxoccurredat3,500–4,000m,andthatofTXn,TX90andTXxrespectivelyhappenedin4,500–5,000,3,500–4,000and3,000–3,500mofelevation.Themaximumwarmingmagnitudeofallcoldnessindexesoccurredat4,500–5,000mexceptforFD,whilethatofthethreewarmthindexesappearedat3,500–4,000m.Thesefeaturesthewiderwarmingmagnitudeofhighaltitudeareascomparedwithlowaltitudeareas(Figs.4.10and4.11).Intermsofextremeprecipitationindex,theregionaltrendsofonlyPRCPTOT,CWDandR10mmshowedaincreasingtrendwiththeriseofelevation,reflectingtheincreaseofwetdayprecipitationandrainydaysinthehighaltitudearea.WhilethenegativecorrelationofCDDwithelevationindicatedthatthedecreaseofconsecutive 1264SpatialandTemporalVariationofClimate…0.060.10.110.180.150.160.180.220.210.40−−−−−−−−−−4.871.792.621.442.543.043.082.953.143.553.443.534.193.184.693.864.625.643.694.78−−−−−−−−−−2.592.160.210.551.000.481.920.251.170.722.110.722.311.111.431.952.271.882.222.29−−−−−−−−−−0.711.43°Cord/10a)0.300.240.280.210.580.640.150.160.240.240.566.360.210.190.842.121.201.292.353.250.071.826.800.151.130.144.520.055.440.24.340.040.034.730.314.710.144.210.220.343.970.180.095.800.470.13.240.290.443.040.470.190.180.180.150.560.230.75−−−−−−−−−−).Copyright(2012),withpermissionfromElsevier2012b0.000.040.180.080.290.241.130.842.684.97−−−−−−−−−Meantrendsperdecadeoftemperatureextremesincategorizedelevationranks(1,5002,000172,500173,00083,500104,00084,50085,000731,000––16–––––––50018–Table4.9Altitude(m)0Stations5001,000id1,5002,000fd2,5003,0003,500gsl4,0004,500txxReprintedfromtheLancet:Lietal.(Valuesforthehighesttrendsincategorizedelevationranksaresetinboldtxntnxtnntx10tx90tn10 4.3DrivingMechanismforClimateExtremes127Fig.4.10Trendmagnitudesoftemperatureextremesversuselevation.ReprintedfromtheLancet:Lietal.(2012b).Copyright(2012),withpermissionfromElsevierdrydaysmainlyoccurredinhighaltitudeareas.TherestoftheextremeprecipitationindexhadmoresharpchangewiththeriseofelevationexceptforSDIIandRX1day,reflectingtheincreaseofrainfallwithaltituderising.Themaximumdecliningmag-nitudeofCDDappearedat3,000–3,500m,andtheregionaltrendsofR99,RX1dayandSDIIoccurredatanaltitudeof3,000–3,500,3,000–3,500and3,500–4,000m,respectively.Inaddition,thesethreeindexesallincreasedwithaltituderising,reflectingtheincreaseofCWDandPRCPTOTinhighaltitudeareawastheresultofR10mmincreasing.ThemaximumincreasingmagnitudeofSDIIisinhighaltitudearea,whereastheminimumoccurredatanaltitudeof1,000–1,500m,suggestingagainthatthestrengtheningofprecipitationintensityandextremeprecipitationeventsresultedfromabovethemainlyappearedinlowaltitudearea(Table4.10).IntermsofR95,R99andRX5day,themaximumincreasingmagnitudeoccurredatabove4,500m,andtheminimumoccurredat3,000–3,500m.Themaximum 1284SpatialandTemporalVariationofClimate…Fig.4.11Trendmagnitudesofprecipitationextremesversuselevation.ReprintedfromtheLancet:Lietal.(2012b).Copyright(2012),withpermissionfromElsevierincreasingmagnitudeofR20mmoccurredatanaltitudeof4,000–4,500m,whiletheminimumwasatlowelevationarea.Onthewhole,thesignificantincreasingtrendofeightindexesappearedinabove3,000m,reflectingthattheincreaseofrainydaysmainlyhappenedinhighaltitudearea.WhiletheincreaseofRX1day,SDII,R95andR99inlowaltitudeareaprovedthattheextremeprecipitationincreasechar-acterizedbythestrengtheningofprecipitationintensitymainlyhappenedinthearea.TheincreasingtrendofRX1day,RX5day,SDII,R20mm,R25mm,R95,andR99primarilyconcentratedinelevationof1,000–3,000m,maybereflectingtheapparenttrendofextremeprecipitationeventsincreasinginthisarea.AsshowninTable4.11,duetothehighfreedomofair,thewarmingmagnitudeofflatstationismaximum,followedinturnbyintermontanestation,valleystationandsummitstation.TheassessmentofPepinandSeidel(2005)ontheimpactof 4.3DrivingMechanismforClimateExtremes12912.7516.4246.70−−0.672.76−0.572.523.31−−0.290.31.10.150.325.720.870.47.805.380.246.682.710.090.305.582.230.650.453.451.659.3617.434.63−−−−−−−0.100.060.260.10−−−0.170.270.080.020.220.040.11−−−−0.570.770.210.140.010.060.160.120.160.460.181.06−−−−−0.110.040.040.050.010.010.800.250.120.147.623.7030.90−−−−0.031.330.110.070.040.710.810.020.072.35−−−−−).Copyright(2012),withpermissionfromElsevier1.652012b0.020.141.080.631.031.053.870.404.321.200.210.815.630.339.440.090.851.580.051.440.840.120.050.182.91−−−−−−12.9110.500.10−0.30−−Meantrendsperdecadeofprecipitationextremesincategorizedelevationranks(mmord/10a)1,5002,000172,500173,00083,500104,00084,50085,000731,000–16––––––––50018–Table4.10Altitude(m)0Stations500cdd1,0001,5002,000rx1day2,500rx5day3,0003,500sdii4,000r10mm4,500ReprintedfromtheLancet:Lietal.(r20mmValuesforthehighesttrendsincategorizedelevationranksaresetinboldR25mmcwdr95pr99pprcptot 1304SpatialandTemporalVariationofClimate…0.030.06–0.070.193.210.243.210.093.842.94––––5.060.250.050.45–––0.180.150.391.842.334.34–1.740.6713.961.24––3.183.820.120.211.480.08°Cormmord/10a)0.01–1.05–2.410.66–0.110.91–1.423.790.160.190.28–0.03–2.953.774.063.22––––0.350.09––0.460.750.450.24––0.460.190.4424.231.07––1.110.820.990.241.310.270.63––––0.280.078.640.20.110.0716.830.070.460.150.165.290.142.528.520.464.62––––).Copyright(2012),withpermissionfromElsevier2.853.533.933.42−–––2012b9.7512.1810.93–––3935Numbercdd35cwdprcptotr10mmr20mmR25mmr95r99rx1dayrx5daysdiiMeantrendsperdecadeofclimateextremesindifferingtopographicaltypes(Table4.11TemperatureextremesSummitstationNumberIntermontanestationtn10FlatstationValleystation352tx10PrecipitationextremestxnSummitstationIntermontanetnn2stationFlatstationfdValleystationReprintedfromtheLancet:Lietal.(0.45idValuesforthehighesttrendsindifferingtopographicaltypesaresetinbold3935tn90tnxtx90txxdtrgsl 4.3DrivingMechanismforClimateExtremes131terraintypestotemperaturechangealsoconfirmedthemorewarmingmagnitudeofsummitstationcomparedwithotherstations.Intermsofprecipitationindex,thesummitstationshowedaapparentdecreasetrendandthemagnitudewasmuchgreater,thenextoneisflatstation,majorofwhichwasonthedecline.Exceptingforthetwoofvalleystationsandthreeofintermontanestations,therestofstationshadarisingtrend.Buttheincreasingtrendisremarkablegreater,especiallywetdayprecipitation(PRCPTOT),heavierprecipitationdays(R20mm),verywetdayprecipitation(R95)andthemaximum5-dayprecipitation(RX5day).Thispatternindicatedthattheapparentinfluenceofterraintoprecipitationchange,reflectedtheincreaseofextremeprecipitationeventswasmainlyoccurredinvalleystationanddemonstratedthatthesignificanteffectoforographicrainfalltoregionalprecipi-tation.Therefore,ithasaveryimportantmeaningtostrengthenthemonitoringresearchoftheextremeprecipitationeventsinvalleyinSouthwesternChinaforthepreventionandcontrolofregionalmeteorologicalanditsrelatedgeologicaldisaster.4.3.3TheComparisonofTemperatureExtremesBetweenUrbanandRuralStationAsshowninTable4.2,fortheTX10,TN10,FDandDTRshowingdecreasetrend,themagnitudeofruralstationwasgreaterthantheurbanstation,buttheurbanstationinpercentageofstationsshowingsignificantdecreasetrendwasgreaterthanruralstation.ExceptforTN90andTNx,theextremetemperatureindexchangesofurbanstationsisgreaterthantheruralstation.TherearesomenumberofstationshavingasignificantwarmingtrendinTN90andTX90ofwarmthindexesbetweenurbanandruralstation,buttheTNxandTXxofruralstationismoregreater.Inaddition,thestationsshowingasignificantwarminginGSL,TNnandTXninruralstationsaremorethanurbanstations.Thepercentageofstationsofcoldnessindex(TN10,FD,TXnandTNn)inurbanstationshowingremarkablewarmingaremorethantheruralstation.Andthestationswherethethreewarmthindexes(GSL,TNxandTXx)performsapparentwarmingtrendinruralstationaremore.Thestationswherethethreenightindexes(TNnandTN10)performsapparentwarmingtrendinurbanstationaremore.Whilehestationswherethethreedaytimeindexes(TXxandTX10)performsapparentwarmingtrendinurbanstationaremore(Table4.12).Themainreasonsofthisdifferencesarethecoldindexeventsgenerallyappearinthewinterwhentheurbanheatislandeffectisthemostobvious;thewarmthindexeventsoccurinthesummerandthewarmingmagnitudeofruralstationsathighaltitudeinsummerisgreaterthantheurbanstationsatlowaltitude.Theresultofabovecomparisonindicatestheregionaltrendsofurbanstationisgreaterthantheruralstationinthestudiedarea.Ifthisdifferenceiscausedbytheurbanheatislandeffect,theinfluenceismainlyreflectedontheminimumtemperature,whichisconsistentwiththeresearchresultofGriffithsetal.(2005)onAsia–Pacificregion. 1324SpatialandTemporalVariationofClimate…Table4.12Trendperdecadeofurban(N=58)andruralstations(N=53),percentageofstationswithsignificantwarmingtrendandthecontributionfromUBIontheregionaltrendsofurbanstationsfortemperatureextremes(°Cord/10a)IndexUrbanstationRuralstationDSDSIRegionalContributionDSDSIRegional(%)(%)(%)trendsrate(%)(%)(%)(%)trendsTX1074125−0.152685472−0.11TN1093880−0.403096850−0.39TXn140240.1427170170.10TNn20780.331060680.30FD98832−0.351898752−0.29DTR81625−0.221583536−0.19TN9072830.3660830.38TX90145550.2627112550.19TXx243100.1416132340.11TNx223500.20170620.21GSL30240.221460530.19Dpercentageofstationswithdecreasetrend,SDpercentageofstationswithsignificantdecreasetrend,SIpercentageofstationswithsignificantincreasetrendSystematicalresearchesGenerally,thedifferenceoftemperaturechangesbetweenurbanandruralstationisdefinedasthecontributionoftheurbanheatislandtotemperaturerisingofcityarea(Jonesetal.2008;Renetal.2008).Ifbasedonthis,theaveragecontributionsoftheurbanheatislandinthestudiedareatocoldindex(TX10,TN10,TXn,TNnandFD)warmindex(TNx,TNn,TN90andTX90)wererespectively16.0and7.9%in1961–2008,andthecontributiontodaytimeindexwashigherthannightindex.Obviously,italsohadagreatercontributiontocoldindex.Thefurtheranalysisfoundthattheurbanheatislandmadetheregionaltrendofdiurnaltem-peraturerange(DTR)increased0.16°Cin1961–2008andcausedthatwarmestdaytemperature(TXx),coldestdaytemperature(TXn)andcoldestnighttemperature(TNn)rised0.11,0.18and0.15°C,respectivelyfrom1961to2008.ThesequenceofcontributionrateofurbanheatislandtoextremetemperatureindexesisTXn>TX90=TXn>TX10>FD>TXx>DTR>GSL>TNn.Aftercomparisonwiththeexistingresearchresult(KimandBaik2002;Choietal.2003;Jonesetal.2008;Renetal.2008)ofsomeregionsintheworld,itisfoundthattheurbanheatislandhasalittlecontributiontothewarmingofurbanstationsinSouthwesternChina.Themainreasonsare:(1)alowlevelofurbanizationinthestudiedarea.Thereareonlythreecitieswherethepopulationismorethanonemillion;(2)thebigaltitudedifferenceofterraininthestudiedareaandthegreaterwarmingmagnitudeofhighaltitudearea.Itindicatesthatthehigherwarmingofurbanstationsmayconfirmthegreatercontributionsoftheurbanheatisland.However,theaboveanalysisisjustasimplecomparisonaboutwarmingmagnitudebetweenurbanandruralstationsbasedontargetpopulation.Soitsresulthasabiglimitation.Thespecificimpactofurbanizationprocesstoextremetemperaturechangesarestillsubjecttofollow-up. 4.4Summary1334.4SummaryThischapteranalyzeddetailedlythespatialandtemporalvariationsandinfluencingfactorsof12temperatureextremesindexesand11precipitationextremesindexesamong110stationinSouthwesternChina.Theresultsareasfollowing:(1)Thetemperatureextremeindexwarmssignificantlyinstudiedarea.MeanTX10,TN10,TXn,TNn,FD,DTR,TN90,TX90,TXx,TNxandGSLallinSouthwesternChinashowedastatisticallysignificantwarmingin1961–2008exceptforID,andallindexesacceleratedtowarmagterthemidof1980s.Thewarmingmagnitudesofcoldnessandnightindexaresignificantlygreaterthanwarmthanddaytimeindex.Theregionaltrendsofstudiedareaisapparentlylessthanthatofotherregionsintheworld.ThepercentageofstationsofTX10,TN10,TXn,TNn,ID,FD,DTR,TN90,TX90,TXx,TNxandGSLperformingsignificantwarmingtrendin1961–2008are36,91,24,77,27,81,50,88,62,88,67and38%.Onthewhole,thestationswithextremetem-peratureindexsignificantlywarmingaremainlydistributedinXizangPlateauandHengduanMountain,andthestationswithnon-significantwarmingtrendordecreasingtrendarelocatedinYunnan–GuizhouPlateauandSichuanBasin.Thewarmingmagnitudeofextremetemperatureindexalsoincreaseswiththeriseofaltitude.Intermsoftheinfluenceofterrain,themagnitudeofflatstationsisthemaximumfollowedbyintermontanestation,valleystationsandsummitstationinturn.(2)Thesignificancelevelofprecipitationextremesindexisquitelow.Therethechangingtrendofonlythemaximum1-dayprecipitation(RX1day),consec-utivewetdays(CWD)andextremelywetdayprecipitation(R99)havepassedthesignificancetest.ThepercentageofstationsofPRCPTOTin1961–2008,SDII,RX1day,R95,R99,RX5day,R10mm,R20mmandR25mmwithsignificantincreasingtrendare25,11,10,10,8,8,15,8and12%,respec-tively.ThepercentageofstationsofCDDandCWDperformingsignificantreductionare8and19%.ThechangesofRX1day,R95,R99,RX5dayandothersreflectsthatthoughtheextremeprecipitationeventsincreasedinrecentyears,thistrendfailedtopassthesignificancetest.Thespatialdistributionofextremeprecipitationindexrevealsthatthesignificantincreaseofrainydaysathighaltitudeandthestrengtheningofrainfallintensityyearbyyear.From1961to2008,theaveragecontributionoftheprecipitationextremesinthestudiedarea(R95andR99)toannualprecipitationis34.2%andkeeprisingtrend,suggestingthattheextremeprecipitationhasamoreandmorecontributiontotheannualprecipitation.ThehighestfrequencyofprecipitationeventsoccursinSichuanBasin,andthecontributionrateofextremeprecipitationreachesto41%oftoannualprecipitation.Themajorextremeprecipitationindexesinflatandsummitstationshaveadowntrend,whilethemajorindexesinvalleyandintermontanestationsareontherise.(3)Thelarge-scaleatmosphericcirculationisthemaincauseofthechangeoftheclimateextremesevents.Insummerandautumn,aanticycloniccirculation 1344SpatialandTemporalVariationofClimate…developsinEurasiaandiscenteredbywesternMongoliaandNorthwesternChina,indicatingtheweakeningofAsianmonsoonsystemfrom1961–1985to1986–2008.Becauseofthis,thestudiedareaiscontrolledbydryandhotairmass,andthenorthlywindbindersthemovingofoceanwarmaircurrenttowardnorthresultinginawidermarginofwarminganddecreasingfrequencyofprecipitation.InthewinterandspringofEurasia,ananticyclonesystemandanabnormalcyclonesystemdevelopsimultaneouslyandarecenteredbyMongoliaandLakeBaikalarea,reflectingthestrengtheningofwestwindintensityfrom1961–1985to1986–2008.Inthecontextofthis,asouthwestwindformsinNorthwesternChinaandthenorthofit.Thiswindfieldpatternreducestheinvasionofwintermonsoonandcoldairtowardsouthandeventuallyleadtothedecreaseofextremecoldeventsandtemperaturerise.From1961–1985to1986–2008,exceptfortheeasternXizangPlateauandthenorthernHengduanMountainwithwatervaporslightlyincreasing,therestregionsbasicallykeepstable.Moreimportantly,theapparentweakeningofmeridionalwindfromformerperiodtolatterperiodconfirmsweakeningmonsooncirculationandwatervaportransportinrecentyears,andpartlyexplainsthenon-significantchangeofprecipitationextremesinthestudiedarea.(4)Thecontributionofurbanheatislandeffecttothewarmingmagnitudeoftem-peratureextremesindexcannotbeignored.Theurbanstationsinregionaltrendoftemperatureextremesindexandpercentageofstationswithsignificantwarmingtrendaremorethantheruralstations.Thepreliminaryanalysisfoundthatthemeancontributionrateofurbanheatislandtothewarmingmagnitudeofcoldnessindex(TX10,TN10,TXn,TNnandFD)andwarmthindex(TNx,TNn,TN90andTX90)ofurbanstationsare16.0and7.9%,respectively.Itscontri-butiontonightindexalsomorethanthatofdaytimeindex.Urbanheatislandcausestheregionaltrendofdiurnaltemperaturerange(DTR)increased0.16°Cin1961–2008andthewarmestdaytemperature(TXx),coldestdaytemperature(TXn)andcoldestnighttemperature(TNn)rised0.11,0.18and0.15°C,respectively.ThesequenceofcontributionrateofurbanheatislandtoextremetemperatureindexesinthestudiesareaisTXn>TX90=TXn>TX10>FD>TXx>DTR>GSL>TNn.ReferencesAguilar,E.,etal.(2005).ChangesinprecipitationandtemperatureextremesinCentralAmericaandnorthernSouthAmerica,1961–2003.JournalGeophysicalResearch,110,23107.Aguilar,E.,etal.(2009).ChangesintemperatureandprecipitationextremesinwesterncentralAfrica,GuineaConakry,andZimbabwe,1955–2006.JournalGeophysicalResearch,114,D02115.Alexander,L.V.,etal.(2006).Globalobservedchangesindailyclimateextremesoftemperatureandprecipitation.JournalGeophysicalResearch,111,D05109.Choi,Y.,etal.(2003).AdjustingurbanbiasintheregionalmeansurfacetemperatureseriesofSouthKorea,1968–99.InternationalJournalofClimatology,23,577–591.doi:10.1002/joc.881. 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Chapter5SpatialandTemporalVariationofSunshineHoursinSouthwesternChina5.1TemporalVariationofSunshineHours5.1.1MeanSunshineHoursIn1961–2008,theannualmeansunshinehoursinSouthwesternChinawas1894handthedailymeansunshinehourswas5.2h.Themaximumannualmeansunshinehourswas3,514hoccurredinShiquanhestationsofXizangAutonomousRegionandtheminimumwas930hoccurredinDujiangyanstationofSichuanProvince.Theannualmeansunshinehoursinsummerandwintermonsoonperiodwere531,483,438,783,956,and949h.Thatofspringandwinterweresignificantlyhigherthanthatofsummerandautumn.Theaccordingmaximumoffourseasonswere932,957,888,2,250,1,720,and1,901h,respectivelyandtheminimumwere236,279,156,90,311and549h.AsshowninFig.5.1,thehighvalueofannualmeansunshinehoursinthestudiedareamainlyoccurredathighaltitudeareas,suchasXizangPlateau,HengduanMountainandYunnanPlateau,whilethelowaltitudeareaslikeGuizhouPlateauandSichuanBasinhadlesssunshinehours.Asamedistributionpatternofannualmeansunshinehourstoyearlyperiodwasshowedbyspring,winter,autumnandwintermonsoonperiod,whereasthelowervalueofsunshinehoursinsummerandsummerperiodhappenedinthewestofSichuanBasin,thesouthofHengduanMountainandYunnanPlateau.Intermsofregionalaverage,annual,spring,summer,autumn,winter,summerandwintermonsoonsunshinehoursinXizangPlateauandHengduanMountainwere2,484,671,564,614,777,1,302and1,188h.ThecorrespondingvalueinYunnan-GuizhouPlateauwere1,678,484,433,484,968,843,and847h,respectively,reflectingthatthesunshinehoursdecreasewiththedeclineofaltitude;thesunshinehoursinwinterandspringofXizangPlateau-HengduanMountainweremorethaninsummerandautumn,whiletherewasfewdifferencebetweentheminYunnan-GuizhouPlateau;thatinsummerandautumnofSichuanBasinwasmorethaninwinterandspring.©Springer-VerlagBerlinHeidelberg2015137Z.Li,StudyonClimateChangeinSouthwesternChina,SpringerTheses,DOI10.1007/978-3-662-44742-0_5 1385SpatialandTemporalVariationofSunshineHours…Fig.5.1Spatialdistributionoftheaveragesunshinehoursduring1961–2008,aannual.bSpring.cSummer.dAutumn.eWinter.fWintermonsoonperiod.gSummermonsonperiod 5.1TemporalVariationofSunshineHours1395.1.2TheInterannualVariationofSunshineHoursAsshowninFig.5.2,theannualmeansunshinehoursreducedattherateof31.9h/10ain1961–2008.Theinterannualvariationwasrepresentedthroughtheincreaseof1960s,thecontinuousdecreaseduring1970–1990andtheriseafterward.Thedecreasingmagnitudein1961–2008was−35.7h/10aandhadpassedthesignif-icancetest,buttheincreasingmagnitudein1991–2008was18.1h/10awhichfailedtopassthesignificancetest.Thischangeisconsistenttothe“darkening”and“brightening”ofmostpartsoftheworldsince1960sconcludedbyobservationdataandsatellitedata,andalsohadasamedecreasingtendency(−19.92h/10a)tosunshinehoursofNorthwesternChinain1961–2007.ButitstendencyismuchdifferentfromthatintheeastandcentralofQinghai-XizangPlateau,wherethesunshinehoursincreasedattherateof49.8h/10ain1961–1982butdecreasedartherateof−65.1h/10a.ItalsowasdifferentfromotherregionsinChinawhichcontinuedtodeclineoverthepassedseveraldecades,reflectingtheregionaldif-ferenceofsunshinehoursvariation(Table5.1).In1961–2008,thedecreasingmagnitudeofspring,summer,autumn,winter,summerandwintermonsoonsunshinehourswere−6.9,−18.2,−2.7,−4.9,−9.3and−20.6h/10a,respectively.Andthechangingmagnitudein1961–1990wereFig.5.2Inter-annualvariationofsunshinehoursinSouthwesternChinaduring1961–2008,aannual,bwinter,cspring,dsummer,eautumn,fWMP,gSMP 1405SpatialandTemporalVariationofSunshineHours…)c),b)bb))))–20102010200820072010a,2010a,2010a,etal.(Yangetal.Yangetal.(Guoetal.(Heetal.–Jiaoetal.(Shenetal.(FanZhenetal.–Duetal.–Youetal.(Chenetal.(Thisstudy28.37.623.122.22623.63.19.32.7−−−−−−−−−73.710.427.416.92513.53.42.711−−−−−−−−−75.718.428.942.55328.124.77.418.21114.39.48.1−−−−−−−−−−−72.914.3206.6104.95.76.911.1−−−−−−−−−11.8144.3–82.957.696.788.3110.466.465.412.234.120.619.931.935.7−−−−−−−−−−−−−18.119992008200520052006199920082005200520052007200819902008––––––––––––––Period19651956Annual196519551965Spring1960Summer19591961Autumn1971Winter1961Sources196119611991’strendsinmanypartsofChina(h/10a)cantatthe5%levelaresetinboldfiSunshinehourTable5.1NorthChinaLiaoningProvinceHebeiProvinceAnhuiProvinceHenaiProvinceJiangsuProvinceShanxiProvinceGuizhouProvinceTibetautonomousregionTheeasternandcentralTibetanPlateauThenorthwesternChina1961SouthwesternChinaValuesfortrendssigni 5.1TemporalVariationofSunshineHours141−11.1,−11,−11,−2.7,−18.4and−18.3h/10a,respectively.Inaddition,thecorrespondingchangemagnitudein1991–2008were11.8,−14.3,9.4,8.1,23.4,and7.2h/10a.Winter,springandwintermonsoonsunshinehoursincreasedin1960s,thendecreasedfor1970–1995andwasontheriseafterward(Fig.5.2).However,autumnsunshinehoursrepresentadowntrendin1961–1990,thencon-tinuedtorisein1991–2008(Fig.5.2).Onthewhole,theannualandseasonalsunshinehoursshowedadeclinetendencybefore1990,thenhadaapparentrise.Thedecreasingmagnitudewasmostsignificantinsummerandsummermonsoonperiod,butthechangingmagnitudeinwinterandwintermonsoonperiodhadnotpassedthesignificancetest.From1961to1990,onlythedecreasingmagnitudeofspringcouldnotpassthesignificancetestandthechangingmagnitudeofspring,summerandwintermonsoonperiodwasremarkablyhigherthanin1961–2008.Whiletheincreasingmagnitudeofonlyspringandwintermonsoonperiodhadpassedthesignificancetest(Table5.1).AsshowninTable5.1,thesunshinehoursinSouthwesternChinawerelessthanthatofotherregionsexceptfortheQinghai-XizangPlateauandNorthwesternChina.Additionally,thereductionofsunshinehoursmainlyoccurredinsummerhalfyear,andthedecreasingmagnitudeofEasternChinawasmuchmorethanthatofWesternChina(Table5.1).ThesunshinehoursinXizangPlateau-HengduanMountainhadadowntrendattherateof−21.3h/10ain1961–2008.Foritsinterannualvariation,itwasonadeclinein1960s,thenhadafluctuatedchangeandsharplydecreaseduntil2000,buthadarisingtrendafter2000.Thechangingmagnitudeof1961–1990and1991–2008werepositive,suggestingaobviousdifferencewiththechangeofSouthwesternChina(Fig.5.3).AstheTable5.2showing,onlythedecreasemagnitudeofautumnandsummermonsoonperiodhadpassedthesignificancetest,andthedifferenceofseasonalvariationwasverysignificant.Springcontinuedtoincreaseafterthedecreasein1960.Insummer,thesunshinehoursincreasedin1961–1980thendecreasedin1981–2008.Itfluctuatedtodeclineinautumnandhadaslowriseinwinterbefore1985,thenshowedawavelikedecreasechange.Whilethechangingtrendissametoannualone(Fig.5.3).In1961–1990,thesunshinehoursinotherseasonsallshowedarisingtrendexceptforsummermonsoonperiod,butallthechangingmagnitudehadnotpassedthesignificancetest(Table5.2).In1991–2008,thespringandsummersunshinehoursignificantlydeclinedandtheincreasingmagnitudeinwinter,summerandwintermonsoonperiodhadpassedthesignificancetest.Onthewhole,therewasabigdifferenceinthevariationofsunshinehourbetweenthisregionandSouthwesternChina;itschangingmagnitudeismuchsmallerandthesignificancelevelwasalsolower.Inaddition,thedecreasemagnitudeinwinterandspringalsoremarkablylessthanthatinsummerandautumn.In1961–2008,thesunshinehourinYunnan-GuizhouPlateaucontinuedtodecreaseandincreasedafterward.Thechangingmagnitudewas−33.1h/10a.Itsdecreasingmagnitudein1961–1990wasbiggerthanthatoftheentirestudiedperiod,anditincreasedattherateof29.3h/10ain1991–2008withasametrendtoSouthwesternChina(Fig.5.4).Inspring,thesunshinehoursincreasedin1960sthendecreasecontinuously;insummer,itsustainedtodeclinebefore2000andhadarisingtendencyafterward;thesunshinehoursinautumnwasonadeclinebefore 1425SpatialandTemporalVariationofSunshineHours…Fig.5.3Inter-annualvariationofsunshinehoursinXizangplateauandHengduanmountainsduring1961–2008,aannual,bwinter,cspring,dsummer,eautumn,fWMP,gSMPTable5.2Sunshinehour’strendsinthreepartsofSouthwesternChina(h/10a)AnnualSpringSummerAutumnWinterWinterSummermonsoonmonsoonXPHM1961–2008−21.3−4.6−8.9−8.1−2.1−7.2−18.91961–199014.74.39.6−11.27.63.5−4.61991–20084.1−0.3−6.88.112.82.87.6SB1961–2008−52.6−6.0−29.3−2.0−13.1−19.1−31.11961–1990−93.1−17.1−36.3−15.3−19.3−15.4−41.61991–200854.646.2−5.96.010.042.53.4YGP1961–2008−33.1−10.6−17.91.9−4.9−7.4−27.81961–1990−51.3−21.5−11.7−182.3−20.5−24.31991–200829.3−7.44.619.81.514.84.6Valuesfortrendssignificantatthe5%levelaresetinbold1990,thenincreasedandinwinteritshowedaslowriseandawavelikedeclineafterward;inwintermonsoonperiod,itincreasedin1960s,thendecreased,butitincreasedagainafter1990.Whilethesunshinehourinsummermonsoonperiodkeptadowntrend(Fig.5.4).Thedecreasingmagnitudeofspring,summerandsummermonsoonperiodhadsucceededinthesignificancetestin1961–2008,and 5.1TemporalVariationofSunshineHours143Fig.5.4Inter-annualvariationofsunshinehoursinYunnan-Guizhouplateauduring1961–2008,aannual,bspring.csummer,dautumn,ewinter,fWMP,gSMPthedecreasingmagnitudeinspringandsummerweregreaterthanthatinautumnandwinter,whilethesummermonsoonwasgreaterthanwintermonsoon.In1961–1990,thespring,autumnandsummermonsoonsunshinehourhadasharpdecline.Otherseasonsshowedaincreasingtrendin1991–2008exceptforspring(Table5.2).AsshowninFig.5.5,theannualmeansunshinehourdecreasedsignificantlybefore1990andincreasedafterward.Itsdecreasingmagnitudein1961–1990wasgreaterthanthatofentirestudiedarea(Table5.2).Thechangingtrendsinspringandwintermonsoonperiodweresametothatinayear.Itcontinuedtodeclineinsummer,winterandsummermonsoonperiod,whileitslowlydecreasedinautumnbefore1985andshowedafluctuatedincreasingafterward(Fig.5.5).In1961–2008,thechangingmagnitudeofonlyspringandautumncouldnotpassthesignificancetest.Allseasonsin1961–1990showedaapparentdecline,butjustspringandwintermonsoonperionsin1991–2008hadpassedthesignificancetest.ThedeclinemagnitudeinspringandautumninSichuanBasinweremuchlessthanthatinsummerandwinter,andthesummermonsoonperionswasgreaterthanthewintermonsoonperiod.Butforincreasingmagnitude,thespringandwinterweregreaterthansummerandautumn(Table5.2).Inconclusion,thechangingtrendofsunshinehourinSichuanBasinandYunnan-GuizhouPlateauaresimilartothatinSouthwesternChina,andboththeirchangingmagnitudeswerehigherthantheregionallevel.However,thechanging 1445SpatialandTemporalVariationofSunshineHours…Fig.5.5Inter-annualvariationofsunshinehoursinSichuanbasinduring1961–2008,aannual,bspring,csummer,dautumn,ewinter,fWMP,gSMPmagnitudeinXizangPlateau-HengduanMountainwasmuchless.Amongthesethreesub-regions,thechangingmagnitudeinSichuanBasinwasgreatestfollowedbyYunnan-GuizhouPlateauandXizangPlateau-HengduanMountaininturn.Asamefeaturealsowasshowninthesignificancelevelofchangingmagnitude.Alltheydecreasedmoresharplyinsummermonsoonperiodthaninwintermonsoonperiod,andtheincreasemagnitudewasopposite.5.2SpatialVariationofSunshineHours5.2.1SpatialDistributionofVariationTrendsinSunshineHoursDuring1961–2008AsshowninFig.5.6,therewere78%ofstationsshowingadecreasesunshinehourin1961–2008among110stationsandthestationpassingthesignificancetestindecreasemagnitudeaccountedfor59%.ExceptforseveralstationsinthesoutheastofHengduanMountainandthesouthwestofYunnanPlateau,themajorstationinstudiedareahadadeclinechange.ThestationswithawidermarginofdecreaseweremainlydistributedinHengduanMountain,GuizhouPlateauandSichuan 5.2SpatialVariationofSunshineHours145Fig.5.6Spatialdistributionofvariationtrendsinsunshinehoursduring1961–2008,aannual,bspring,csummer,dautumn,ewinter,fWMP,gSMP 1465SpatialandTemporalVariationofSunshineHours…Basin,whileadroporaremarkedrisecouldbefoundinthestationssituatedinXizangPlateau.Duringtheresearchedperiod,abort79%ofstationsexhibitedadecreaseinspringsunshinehour,butsignificantdropwasshowedin32%ofstationsamong110stations.Thestationswithnon-significantdropchieflywerelocatedinXizangPlateau,HengduanMountain,andGuizhouPlateau,whilethestationswithaincreasingtrendweresituatedinXizangPlateauandthewestofYunnanPlateau(Fig.5.6).Insummer,therewereapproximately86%ofstationshavingadecreasingchangeinsunshinehour,buttherewereonlyahalfamongthemdeclinedsharply.Mostobviously,thestationwithasharpdropweremainlydistributedinthelowaltitudearea,likeGuizhouPlateauandSichuanBasin.Whereas,thestationsinhighaltitudeareahadanon-significantdecreaseorincrease(Fig.5.6).Thesunshinehourinstudiedareaappearedalittledropinautumn,justthestationsinHengduanMountainshowedaremarkabledecline,accountingfor23%ofallstations.WhilethestationsinsouthwesternYunnanPlateau,southeasternHengduanMountain,andXizangPlateauincreased,accountingfor38%ofstations(Fig.5.6).Therewere68%ofstationsreducedinwintersunshinehour,butonly28%ofthe110stationshadpassedthesignificancetestinapparentdecline,whichweremainlydistributedinthelowaltitudeares,suchasGuizhouPlateauandSichuanBasin.However,themoststationsinXizangPlateau,thesouthofHengduanMountainandthesouthwestedgeofYunnanPlateauhadaincreasetrend(Fig.5.6).ExceptforthesomestationsinXizangPlateauandHengduanMountain,only84%ofstationsperformedareducetrendinsummermonsoonsunshinehour,butonly53%ofthemhadpassedthesignificancetestinthisfactor,whichweremainlysituatedinGuizhouPlateauandSichuanBasin(Fig.5.6).ThewintermonsoonsunshinehourofstationsinXizangPlateau,HengduanMountainandthesouthwestofYunnanPlateauaccountingfor30%ofallstationswasontherise,andabout30%ofstationslocatedinGuizhouPlateauandSichuanBasindecreasedsharply(Fig.5.6).Asawhole,thedecreaseofsunshinehourinSouthwesternChinaprincipallyappearedinlowaltitudearea,especiallyinGuizhouPlateauandSichuanBasin.Whilemoststationsinhighaltitudeareareducedslightlyorhadarisingtrend.5.2.2SpatialDistributionofVariationTrendsinSunshineHoursBetween1961–1990and1991–2008Inordertofurtherrecognizethechangingfeaturesofthesunshinehourinthestudiedarea,thisstudyanalyzedtheregionaltrendofallstationsbetween1961–1990and1991–2008.AsshowninFig.5.7,thepercentageofstationswithadowntrendinannualmeansunshinehourwas68%,buttherewere37%ofthempassingthesignificancetestwhichweresituatedinYunnanPlateau—Plateauand 5.2SpatialVariationofSunshineHours147Fig.5.7Spatialdistributionofvariationtrendsinsunshinehoursduring1961–1990,aannual,bspring,csummer,dautumn,ewinter,fWMP,gSMP 1485SpatialandTemporalVariationofSunshineHours…SichuanBasin.Whereasthestationswithincreasingtrendwerelocatedinhighaltitudearea.ExceptforsomestationsinXizangPlateauandHengduanMountain,approximately78%ofthestationsreducedinspringsunshinetime.ThestationsinYunnanPlateau—PlateauandSichuanBasinshowedaremarkabledecreaseandaccountedfor29%ofallstations.Thepercentageofstationswithadeclinetrendinsummersunshinehourwas62%,butonly25%ofthemhadpassedthesignifi-cancetest.Moreover,thestationsinizangPlateauandHengduanMountainappearedarisingtendency(Fig.5.7).Inautumn,thestationsshowingdecreasingsunshinehourweremostinayear.ExceptforsomestationsinXizangPlateau,about80%ofthestationsperformingareducingtrendandthestationswithasharpriseweremainlydistributedinlowaltitudearea.Approximately45%ofthestationsinGuizhouPlateauandSichuanBasinhadadropinwintersunshinehour,and13%ofstationswitharemarkabledecreasewereprimarilysituatedinSichuanBasin.Insummerandwintermonsoonperiod,thespatialdistributionofvariationtrendsinsunshinehourswassimilartotheyearly,andtherewererespectively70and68%ofstationsshowingadown-trend.Butthereonly28and20%ofstationsdropdownsharply(Fig.5.7).Overall,during1961–1990,thestationsexhibitingadecreasetrendweremainlyinlowaltitudearea,whilethestationswithincreasetrendwerelocatedinhighaltitudearea.Thepercentageofstationshowingadroporsharpdecreasewaslessthanthatof1961–2008.In1991–2008,theannualmeansunshinehourofabout61%ofstationsincreased,butonly30%increasedsignificantlyamongthem.MoststationsinGuizhouPlateaushowedadroppingtrend,andthereststationswithadecreasingtrendscatteredinotherregionsexceptforYunnanPlateau(Fig.5.8).Inspring,about58%ofstationsshowedaincreasingtrend,butonly23%ofthemhadpassedthesignificancetestwhichweremainlydistributedinGuizhouPlateauandSichuanBasinandafewstationswereinXizangPlateauandHengduanMountain.WhilealmostallstationsinYunnanProvincereducedsignificantly(Fig.5.8).Summersunshinehoursofonly43%ofthestationsincreased,andthestationswithsignificantincreasejustaccountedfor11%whichlocatedinXizangPlateauandYunnanPlateau,whilethestationsinHengduanMountain,GuizhouPlateauandSichuanBasindecreased.ThesunshinehourinthewholeYunnanPlateauincreased,andthemoststationsinXizangPlateauandHengduanMountainalsoshowedarisingtrend,accountingfor69%ofallstations.Buttherewereonly27%ofstationshavingaremarkablerise(Fig.5.8).Inwinter,thestationswithdecreasingtrendwerelocatedinGuizhouPlateauandthesouthofHengduanMountain.Whilethereabout63%ofthestationsshowedanincreasingtrend,asharprisingjustappearedin19%ofstations.Insummerandwintermonsoonperiod,thespatialdistributionofvariationtrendsinsunshinehourswassimilartotheyearly,andtherewererespectively67and53%ofstationsshowingauptrend.Butthestationspassingthesignificancetestonlyhad28and20%(Fig.5.8).Inconclusion,themostapparentfeatureinthisperiodwasthatthestationswitharisingtrendincreasedapparentlyinlowaltitude. 5.2SpatialVariationofSunshineHours149Fig.5.8Spatialdistributionofvariationtrendsinsunshinehoursduring1991–2008,aannual,bspring,csummer,dautumn,ewinter,fWMP,gSMP 1505SpatialandTemporalVariationofSunshineHours…5.3DrivingMechanismforSunshineHours5.3.1RelationshipBetweenWindSpeedandSunshineHoursRelatedresearchesthoughtthatthewindspeedisthemajorreasonofsunshinehourchanging(Rodericketal.2007,2008;Rayner2007;Robertetal.2010).TwocharactersoftemporalandspatialvariationinwindspeedandsunshinehourinSouthwesternChinacanbeshowedasfollows:(1)asignificantcorrelationandsimilarchangingtrend.In1969–2008,therewasasignificantpositivecorrelationbetweenwindspeedandsunshinehourinstudiedareaexceptforinautumn,andthecorrelatedlevelofthembecamehigherin1969–2000(Table5.3).Inaddition,asamechangingtrendofwindspeedandsunshinehourindicatedthecloserela-tionshipbetweentheweakeningofspeedwindandthedecreaseofsunshinehour(Fig.5.9).Theinfluenceofwindspeedtosunshinehourrepresentedaregionaldifference.ThewindspeedandsunshinehourshowedasignificantlypositivecorrelationinXizangPlateau-HengduanMountainexceptforyearlyandwinter,becausetherewerelessprecipitationandmoresunnyday,sowindspeedhadalittleinfluencetosunshinehour.Whileannual,winterandwintermonsoonwindspeedTable5.3Relationshipbetweenwindspeedandsunshinehoursduring1969–2008(h/10a)AnnualSpringSummerAutumnWinterSummerWintermonsoonmonsoonTrendin1969–2000(h/10a)−62.40−15.90−30.90−6.60−11.30−26.00−37.50Trendin2001–2008(h/10a)−4.80−5.90−15.8017.80−22.60−56.9026.80Trendinnon-windydays−41.54−7.38−20.50−3.09−7.06−12.96−24.79during1969–2008(h/10a)Stationswithdecreasingtrend0.820.800.860.690.760.800.86innon-windydaysTrendinwindydaysduring−29.90−8.14−12.99−3.41−2.56−7.25−20.611969–2008(h/10a)Stationswithdecreasingtrend0.760.790.870.560.610.630.82inwindydaysCorrelationcoefficientswith0.580.410.530.160.280.460.52windspeedin1969–2008Correlationcoefficientswith0.670.470.610.200.380.600.60windspeedin1969–2000Correlationcoefficientswith−0.270.39−0.160.01−0.84−0.67−0.13windspeedin2001–2008Correlationcoefficientswith0.210.460.300.340.250.510.62windspeedinXPHMin2001–2008Correlationcoefficientswith0.290.070.070.220.360.310.26windspeedinYGPin2001–2008Correlationcoefficientswith0.310.310.010.210.390.340.49windspeedinSBin2001–2008Valuesfortrendssignificantatthe5%levelaresetinbold 5.3DrivingMechanismforSunshineHours151Fig.5.9Variationofannualmeansunshinehoursandwindspeedduring1969–2008.ReprintedfromLietal.(2012),withkindpermissionfromSpringerScience+BusinessMediahadaapparentlypositivecorrelationinYunnan-GuizhouPlateau(Fig.5.3).ThewindspeedinSichuanBasinshowedasignificantlypositivecorrelationwiththesunshinehoursexceptforsummerandwinter.Thesedifferencesindicatedthattheeffectofwindspeedtosunshinehoursinhighaltitudeareamainlyhappenedinsummerhalfyear,buttolowaltitudeoccurredinwinterhalfyear.Inaddition,boththeydidnotshowaapparentlypositivecorrelationinsummerandautumnofYunnan-GuizhouPlateauandSichuanBasinfrom1969to2008.In2001–2008,theannualandseasonalvariationsofwindspeedandsunshinehourrevealedanegativecorrelation,andthesunshinehoursacceleratedtodecreaseinwinterandwintermonsoonperiod,whichreflectedtheregionaldifferenceofinfluenceofwindspeedtosunshinehours.(2)Asameregionaltrendsofsunshinehourswithwindspeedhadbeshownbyallstations.Thesunshinehourin1969–2000decreasedmuchmoresharplythan2001–2008whenthesunshinehoursshowedarisingtendencyinautumnandsummermonsoonperiod(Fig.5.3).Thereststationsshowedadecreasingtrendin1969–2000exceptfor11stationsinXizangPlateauandYunnan-GuizhouPlateau,and65%ofstationsdeclinedsignificantly.In2001–2001,nearlyhalfofstationsincreasedinsunshinehourandabout32%ofthestationhadpassedthesignificancetest.Furthermore,thedecreasingmagnitudeof10%ofthestationswerelessthanof1969–2000.ThestationswithaincreasingtrendaremainlydistributedinXizangPlateau,thecentralofHengduanMountain,thecentralofYunnanPlateauandGuizhouPlateau(Fig.5.10).Inconclusion,windspeedandsunshinehourshowedsignificantspatialandtemporalcorrelation,provingtheinfluenceofwindspeedtosunshinehour.Inordertofurtheranalyzetheimpactofwindspeedtosunshinehour,thisstudydivided110stationsintotwotypesbasedonwhetherannualmeandailywindspeedisgreaterthan1.5m/sandmakesananalysis.Theyare62stationswherethedailymeanwindspeedisgreaterthan1.5m/s(windeddays)and48stationswherethedailymeanwindspeedislessthan1.5m/s(windlessdays).AsTable5.3showing,in1969–2008,thedecreasingmagnitudeofsunshinehoursinannual,spring, 1525SpatialandTemporalVariationofSunshineHours…Fig.5.10Spatialdistributionofsunshinehours’variationtrendsduringa1969–2000andb2001–2009summer,autumn,winter,summerandwintermonsoonwererespectively−41.54,−7.38,−20.50,−3.09,−7.06,−24.79and−12.96h/10ainthestationsofstudiedareawherethedailymeanwindspeedwerelessthan1.5m/s.Whilethecorre-spondingvaluesofannualandseasonalwindspeedwererespectively−29.90,−8.14,−12.99,−3.41,−2.56,−20.61and−7.25h/10ainthestationswherethedailymeanwindspeedweregreaterthan1.5m/s.Mostapparently,thesunshinehourofstationswherethewindspeedwaslessthan1.5m/sdecreasedmuchmoresharplythanthestationswherethewindspeedwasgreaterthan1.5m/s,andthepercentageofstationshavingadecreasingannualandseasonalsunshinehoursalsoshowedasamecharacteristic.ThisconclusionconfirmedagainthatwindspeedisoneofmaindrivingforcesofsunshinetimechangesandalsosuggestedthattheweakeningofwindspeedreallyisthedirectandstronginfluencefactorofthereductionofsunshinehourinSouthwesternChina.Infact,itisimpossiblethattheweakwindspeedblowsawayclouds,aerosols,andotherairpollutionintheair.Sotherelationshipbetweenwindspeedandthepossiblematerialsintheairwhichmayinfluencetheradiation,likecloudscoverandatmosphericaerosolsisoneofthemajorphysicalprocessesofsunshinehourchangeinthestudiedarea.Moreover,relatedstudieshaveconfirmedthatthewindspeedintheairplaysanimportantroleoncleaning.ThestudyofFuetal.(2008)foundthatYangtzeriverDeltaregionoccurredseverepollutionduetotheabnormalstagnationofair,whenthedailymeanwindspeedislessthan1.0m/s.SatheeshandMoorthy(2005)alsothoughtthatthewindspeedisamostinfluentialfactorofthechangeofregionalatmo-sphericaerosolconcentration.ThestudyofYangetal.(2008a,b,c)alsoconfirmedthatweakeningwindspeedisthemainreasonofthereductionofsunshinehour. 5.3DrivingMechanismforSunshineHours1535.3.2TheRelationshipBetweenRelativeHumidityandSunshineHourAsshowninFig.5.15,thehumidityhadafluctuatingdecreasefrom1961to2008inSouthwesternChina.Thereinto,itkeptastablestate,thenincreaseduntil2000andappearedasharpdropafter2001.Thedecreasingmagnitudewas−2.24%/10aandhadpassedthesignificancetest(Table5.4).Theannualmeanhumidityandsunshinehourshowedaobviouslyoppositetrendsduringtheresearchedperiod(Fig.5.11)whichalsobeshownfromtheirsignificantlynegativecorrelation.Inaddition,thehumidityandsunshinetimechangeshadasignificantlynegativecorrelationbetween1961–1990and1991–2008(Table5.4),suggestingthatthehumidityisanotherinfluencingfactorofsunshinehourchange,becausethewatervaporintheaircanstronglyweakenthesolarradiationbyabsorbing,scatteringandreflection,etc.Asametrendisalsodisplayedbetweenseasonalandannualhumiditychange.Theyalldecreasedsignificantlyin2001–2008,andthedecreasemagnitudeismaximuminwinterandminimuminspring.Theseasonalchangealsohadaapparentlynegativecorrelationwithsunshinehours,especiallyinwinterandspringthecorrelationcoefficientisgreatest(Fig.5.4),whichconfirmedagaintheimportanteffectofhumiditytoregionalsunshinehours.Theannualmeanhumidityslightlyincreasedin1961–2008inXizangPlateau-HengduanMountain,andsharplyincreasedinsummer,winterandwintermonsoonperiod,butreducedinspring,autumnandsummermonsoonperiod(Table5.4).AsshowninFig.5.11,theannualmeanhumidityandsunshinehourhadreversechangesinXizangPlateau-HengduanMountain,andtheannualandseasonalsunshinehourhadasignificantlynegativecorrelationwithhumidity,whichindi-catedtheapparentweakeningofhumiditytosunshinehouratthehighaltitudearea(Table5.4).TheannualmeanhumidityinYunnan-GuizhouPlateaucontinuedtodecrease,sametoseasonalchange(Fig.5.11).Thehumidityhadasignificantlynegativecorrelationwithsunshinehour,andthecorrelationcoefficientsuggestedthattheeffectofhumiditytowinterandspringwasgreaterthansummerandautumn.,becausetherewerelittlecloudcoverinwinterandspring.Butthesharpwarming,especiallynightwarming,leadedtothestrengtheningofevaporationandtheweakeningofcondensationofwatervaporandfurtherresultedintherelativeincreaseofhumidityduringthedaytime,evenultimatelyenhanceitsabilitytoweakenthesolarradiation.TheannualandseasonalhumidityinSichuanBasinslowlyrosebefore1990anddeclinedafterward.Itschangehadasignificantlynegativecorrelationwiththesunshinehour,becauseduetothespecialterrain,moreairrelativehumidityandfoggydaysofthisregionswouldgreatlyweakenthesolarradiation,therebyreducingthesunshinehours(Table5.4).Inconclusion,thereversetrendandsignificantlynegativecorrelationbetweenhumidityandsunshinehourinthestudiedareaverifiedthathumidityisanotherinfluencingfactorofsunshinehourchanges,andthesharpreductionafter1990sundoubtedlyisthekeyreasonoftheincreasingofsunshinehouratthesameperiod. 1545SpatialandTemporalVariationofSunshineHours…0.400.252.140.320.630.290.200.620.520.590.050.53−−−−−−−−−−−−2.040.490.620.640.600.420.390.74−−−−−−−−2008inSouthwesternChinaanditsthreesub-regions–2.450.630.430.540.580.620.430.560.700.55−−−−−−−−0.470.172.190.200.150.360.870.410.010.30.200.420.560.710.030.440.63−−−−−−−−−−−0.350.362.240.510.560.010.510.770.660.420.600.300.65−−−−−−−−−−−−0.031.670.470.330.650.710.630.760.480.72−−−−−−−−−−0.200.012.240.170.600.140.320.630.450.530.120.50−−−−−−−−−−−2008199020082008200820080.07200819900.342008200820082008––––––––––––cantatthe5%levelaresetinboldfiPeriod1961Annual19911961Spring1961Summer1961Autumn1961Winter19911961Wintermonsoon19611961SummermonsooncientfiTherelationshipbetweenannualmeansunshinehoursandrelativehumidityduring1961(%/10a)Table5.4TrendsSouthwestChinaXPHM1961YGPSBCorrelationcoefSouthwesternChina1961XPHMYGPSBValuesfortrendssigni 5.3DrivingMechanismforSunshineHours155Fig.5.11Variationofannualmeansunshinehoursandrelativehumidityduring1961–2008inSouthwesternChinaanditsthreesub-regions.aSouthwesternAsia.bXizangplateau-hengduanmountains.cSichuanbasin.dYunnan-Guizhouplateay5.3.3TheComparisonofSunshineHoursBetweenUrbanandRuralStationsAnumberofresearchesathomeandabroadattributedthedecreaseofsunshinehourstotheseriousatmospherepollutioncausedbyrapidurbanizationprocessandincreasingconcentrationofatmosphericaerosols(Xuetal.2006a,b;Qianetal.2002;Wangetal.2004;Huangetal.2006;Luetal.2007).Inordertoanalyzetheimpactofurbanizationprocess,thisstudycomparestheregionaltrendsbetweentheruralandurbanstations.AsshowninTable5.5,thechangingtrendsofannualandseasonalsunshinehoursinurbanstationsweregreaterthaninruralstationsin1961–2008,andtheautumn,winterandthewintermonsoontrendshadnotpassedthesignificancetest.Theannualspring,summer,winterandwintermonsoonsunshinehoursinurbanstationsincreasedmoresharplythaninruralstationsin1991–2008,andthesummertrendsalsowasgreaterthanthatofruralstations.Moreover,thesunshinehourinurbanstationsshowedadecreasedtendencywhiletheruralstationwasontherise.Obviously,aapparentdifferencecanbeshownfromthechangingtrendsofurbanandruralstations(Fig.5.12).Theannualsun-shinehoursofurbanstationsin1961–2008continuedtoreduce,whiletheruralstationssuccessivelyappearedanincreasein1960s,astablestatein1970–1985,adecreasein1985–2000andaslowriseafterward.Theseasonalchangeinsunshinehourofurbanstationsalsoshowedacontinuousdrop,whereas,inruralstationsthe 1565SpatialandTemporalVariationofSunshineHours…2008)–1.60.310.631.450.230.730.45Trends(1991−cientficoefDSD38Correlation402542160.630160.5728120.553090.3312410.290.38200.632008)–cantdecreasetrend2.180.740.980.190.220.571.6fiRuralstationTrends(1961−−−−−−−2008)–2.351.781.430.860.852.780.65Trends(1991−−cientfiisthepercentageofstationwithsignicoefSDcientsandpercentageofstationswithnegativeorpositivetrendsforsunshinehoursinurbanandruralstationsoffiDSD50Correlation494155200.6539390.4747140.3348190.2250.32530.52390.42008)–3.370.671.970.360.781.252.67UrbanstationTrends(1961−−−−−−−Trends,correlationcoefispercentageofstationwithdecreasetrend,Table5.5SouthwesternChina(h/10a)AnnualSpringSummerAutumnWinterWintermonsoonSummermonsoonD 5.3DrivingMechanismforSunshineHours157Fig.5.12Inter-annualvariationofannualmeansunshinehoursinurbanstationsandruralstationsduring1961–2008winter,springandwintermonsoonsunshinehourhadaslightincreasein1960sfollowedbyadecrease.Andbefore1980thesummer,autumnandsummermon-soonsunshinehourexhibitedaslightriseorastablestate,butdecreasedfrom1980to2000andwasontheriseafterward.Onthewhole,thechangetrendofurbanstationswassimilartothatofYunnan-GuizhouPlateauandSichuanBasin,whilethechangetrendofruralstationswassimilartothatofXizangPlateau-HengduanMountainbecausetheruralstationsweremainlysituatedinthisregion.Thereweremoreurbanstationsshowingadecreasingtrendinannualandseasonalsunshinehoursin1961–2008comparedwiththeruralstations,andthemajorityofstationswithsignificantdecreasewereurbanstations.Inaddition,nomatterwheretheurbanorruralstations,bothannualandseasonalsunshinehourhadasignificantlypositivecorrelation,whichsuggestedagainthatwindspeedisaimportantinflu-encingfactorofsunshinehourinSouthwesternChina.Ingeneral,theinfluenceofurbanizationonsunshinetimemainlywasshownbyenvironmentaleffectsresultedfromtheincreaseofatmosphericaerosolconcentrationincludingdirecteffectandindirecteffect.Thedirecteffectrefersthattheatmosphericaerosolnotonlyscatteredsolarradiationbutalsoenhancedthereflectivityofshortwaveradiation,eventuallyreducedtheradiationorsunshinehour.Indirecteffectrefersthatascloudcondensationnuclei,theaerosolchangefeatureslikecloudcover,eventuallyleadtothewidermarginofcloudalbedosoastoreducethesurfacesolarradiation(Quaasetal.2004).Therefore,themostdirectexpressionoftheimpactofurbanizationonsunshinehouristhatincreasingaerosolconcentrationwillleadtothereductionofsunshinehour.ThestudyofGuoandRen(2006)onsunshinehourinSoutheasternChinaandTianjinProvincedemonstratedthatthecontinuousincreaseofatmosphericaerosolisthemainreasonofthereductionofsunshinehoursinaboveregions.Alargenumberofresearchesalsoconfirmedthattheatmosphericpollutionworsenedandeventuallyleadedtotheapparentincreaseofatmosphericaerosolconcentrationinthecontextofrapideconomicdevelopmentduring1961–2000,especiallysince1980s(Fanetal.2005).Since1961,theenergyconsumptionalsoshowasignificantincreaseinthetrendinSouthwesternChina. 1585SpatialandTemporalVariationofSunshineHours…Fig.5.13ThevariationofenergyconsumptioninSouthwesternChina.ReprintedfromLietal.(2012),withkindpermissionfromSpringerScience+BusinessMediaAccordingtothestatisticalyearbook,theenergyconsumptioninChongqingof1949–2004,Sichuanof1957–2004,YunnanandGuizhouof1978–2004,especiallyinthe1980sincreasedsignificantly.Andtheenergyconsumptionofaboveprov-incesbefore2004were42.6,28.3,9and4.6timesasmuchasthatof1949,1957,and1978,respectively(Fig.5.13).Underthisbackground,thedischargesofindustrialwastegas,industrialsulfurdioxideandindustrialsootallsignificantlyincreasedinSouthwesternChina(Table5.6),whichreflectedthedeteriorationoftheairpollutioninthestudiedareaandtheincreaseofconcentrationofatmosphericaerosoltosomeextent.Whatneedtobestressedisthatthedischargesofatmosphericpollutantsinstudiedareaappearedareducetrendinrecentyearsunderthestrictairpollutioncontrol(Table5.6),whichisbeneficialtoreducetheconcentrationofatmosphericaerosol.However,thesunshinehourinstudiedareahadshownaincreasingtrendfrom1990sinsteadofanoppositetrendtoenergyconsumption.Thecoal-firedheatingofmostareasinChinageneratedtheconcentrationofatmosphericaerosolinwinterwassignificantlyhigherthanthesummer,inotherwords,theinfluenceofaerosolconcentrationonthesunshinehourinwinterwasusuallygreaterthaninsummer(Anetal.2000;Maetal.2005;Niuetal.2006;Wuetal.1999;Yuetal.2002).AsshowninTable5.5,thedecreasingmagnitudewasmaximuminsummersof1961–2008eitherinurbanstationorinruralstation.From1991to2008,thesunshinehourinsummerinbothurbanandruralstationshowedadeclinetrend.Althoughthewintersunshinealsohadadecreasingtrend,themagnitudewasapparentlylessthansummerandautumn.Inaddition,acommon 5.3DrivingMechanismforSunshineHours159441010××4.317441010××3.624441010××4.9304410200810×–×325.8441010××2.119.4441010××216.3441010××1.72602732912,2203332,5587.63072,4382762,7791638217994104×10×1.664410×10×1.3326215488.7441010××1.34.1441010××1.12.7410×1.34102012),withkindpermissionfromSpringerScience+BusinessMedia×19901199519982221999154200010011720021072003200413320051502006122200712320081212009114AtmospherepollutiondischargeandcontrollingindustrialwastegasinSouthwesternChinaduring1990Yuan))43mtons)tons))2844Table5.6YearTotalvolumeofindustrialwastegasdischarge(10Totalamountofindustrialsulfurdioxidedischarge(10Totalamountofindustrialfumesdischarge(10Areaofsootcontrolzones(kmTheinvestmentcostsoncontrollingindustrialwastegas(10ReprintedfromLietal.( 1605SpatialandTemporalVariationofSunshineHours…patternwasthattheaerosolconcentrationofurbanregionwassignificantlyhigherthanthatofsuburbs,andthatofbigcitieswashigherthanmediumandsmallcities.ThebigcitiesofSouthwesternChina,suchasGuiyangandKunminghadthehigherdecreasingmagnitudeofsunshinehourin1961–2008.Guiyangwas−120.9h/10aandKunmingwas−108.4h/10a.WhilethesunshinehourofKunmingin1991–2008increasedattherateof16.5h/10a,andthedecreasingmagnitudeofsunshinehourinGuiyangreduced65.9h/10acomparedwith1961–1900.Thephenomenonthatsunshinehourdidnotdecreasewiththeaccelerationofurbani-zationprocessmaysuggestedthefaintinfluenceofurbanizationprocess.Moreimportantly,since1990s,theremarkableachievementsinthecontrolofatmo-sphericpollutionhadbeenmadeinthetwocities,andthedischargeofindustrialfumes,industrialdustandindustrialsulfurdioxidedecreasedyearbyyear(Fig.5.14).Atthesametime,theremovalofindustrialfumes,industrialdustandindustrialsulfurdioxideincreasedyearbyyear(Table5.7).Basedonthis,itwasdeducedthattheprominentachievementsofatmosphericpollutioncontrolhadaFig.5.14ThedischargingatmosphericpollutesinGuiyangandKunmingduring2000–2008Table5.7ControllingonatmospherepollutiondischargeinKunmingandGuiyangduring2003–20082003200420052006200720082008KunmingTotalamountofindustrial32.636.342.542.055.063.259.3sulfurdioxidedischarge(104tons)Totalamountofindustrial62.562.786.5105.6125.1125.2130.7fumesdischarge(104tons)Totalamountofindustrial78.268.765.741.042.8dustdischarge(104tons)GuiyangTotalamountofindustrial8.28.29.115.014.624.118.8sulfurdioxidedischarge(104tons)Totalamountofindustrial12.713.513.684.999.595.5110.9fumesdischarge(104tons)Totalamountofindustrial30.433.333.632.241.4dustdischarge(104tons) 5.3DrivingMechanismforSunshineHours161positiveeffectontheincreaseofthesunshinehourinrecentyears.Aconclusioncanbemadefromtheaboveanalysisthattherapidurbanizationprocessisnotthemaininfluencingfactorofdifferencesbetweenurbanandruralstationinchangingmagnitudeofsunshinehour.AndthebasicreasonisthattheurbanstationsaremainlylocatedinYunnan-GuizhouPlateauandSichuanBasinwherearethewidermarginofdecreaseoccurredin1961–2008.Furthermore,thestationsatlowaltitudealsohadasignificantincreasein1991–2008(Figs.5.6,5.7and5.8).5.3.4CorrelationwithSunshineHourandOtherMeteorologicalFactorsInordertofurtherunderstandtheinfluenceofmeteorologicalfactorstosunshinehours,thisstudyanalyzedthecorrelationin1961–2008withannualdownwardsolarradiationfluxabsorbedbygroundsurface,totalareaofthecloud,watercontentofthecloudsandsunshinehourbyusingthereanalysisdata.AsshowninFig.5.15,theannualmeandownwardsolarradiationfluxabsorbedbygroundsurfacedecreasedin1980sandcontinuedtoincreaseafter1990.Thistrendwassametothatofsunshinehour.Inaddition,theirstatisticallysignificantpositivecorrelationlevelalsosupportedit(Table5.8),andevidencedagaintheincreasingFig.5.15VariationsofothermeteorologicalfactorsinSouthwesternChina 1625SpatialandTemporalVariationofSunshineHours…Table5.8Correlationcoefficientsbetweensunshinehoursandprecipitation,downwardssolarradiationfluxandrelativehumidityontheannualandseasonalbasisinSouthwesternChinaduring1961–2008PeriodAnnualWinterSpringSummerAutumnWinterSummermonsoonmonsoonPrecipitation1961–2008−0.29−0.52−0.29−0.73−0.31−0.48−0.4Downwards1979–20080.770.750.270.460.620.550.25solarradiationfluxValuesforcorrelationcoefficientssignificantatthe5%levelaresetinboldtrendofsunshinehoursince1990sinSouthwesternChina.Intermsoftotalareaofcloud,itshowedaslightlywavelikechangein1961–2008,andbecamestableafter1980(Fig.5.15).Themaximumareaofcloudsis72%,andtheminimumis66%.Thisfaintchangehadabigdifferencefromthechangingtrendofsunshinehourinthestudiedarea.However,alargenumberofstudiesthoughttheincreaseofcloudcovewillleadtothelesssunshinehour.Forexample,theincreaseofcloudcovecausedthatthesunshinehoursinthecentralandeastofQinghai-XizangPlateaudecreasedyearbyyearsince1983(Youetal.2010a,b).Kaiser(1998,2000)analyzedthechangeofcloudcoverof196stationsin1954–1996andfoundthatmoststationsshowedadecreasingtrend.Qianetal.(2007)analyzedthetotalcloudcoveandlowcloudcoverofChinafrom1954to2001byusingtheobservationdataof537stationsandgotasameconclusion.TheexistingresearchesoncloudcoveralsopointedoutthatthetotalcloudcoverinmostareasofTibetanautonomousregionshowedatrendofsignificantreductionin1971–2008(TangandLi2003).Thetotalcloudcoveandlowcloudcoverof85stationsinSouthwesternChinaexcludingXizangProvinceexhibitedadecreasingtrendin1960–2005(Zhangetal.2011a,b).Basedonthis,itispossiblethatthereductionofcloudcoverhasbeneficialeffectstothesunshinehourinstudiedareainrecentyears,butthedetailedinfluencemechanismneedstobeanalyzedbymeansofobservationdata.Thecloudwatercontentincreasedcontinuouslyafterdecliningin1960s,whichisjustoppositetothechangeofsunshinehour(Figs.5.16and5.17).Moreimpor-tantly,asignificantlynegativecorrelationwithannualandseasonalsunshinehourFig.5.16Variationofannualmeansunshinehoursandcloudwatercontentduring1961–2008inSouthwesternChina 5.3DrivingMechanismforSunshineHours163Fig.5.17Differenceoftotalcloudcover(a)andcloudwatercontent(b)between1961–1970and1971–1980,anddifferencesofthedownwardssolar-radiationflux(c)andrelativehumidity(d)from1981–1990to1991–2000at300hPainSouthwesternChinaandprecipitationwasshown,especiallyinsummer(Table5.8),indicatingagaintheimpactofprecipitationandwatervaporcontentintheaironthesunshinehour.Becausethisregionisamonsoonclimatezone,theprecipitationandcloudydaysmainlyconcentratedinsummerandautumn,whichalsopartlyexplainsthewidermarginofreductionofsunshinehoursinthesetwoseasons,particularlythesummersunshinehourin1991–2008significantlyreduced.Inaddition,theanalysisofthereanalysisdatarevealedthatannualcloudareashowedaincreasingtrendfrom1961–1970to1971–1980andthecloudwatercontentalsoincreased.Thesefea-turesmaypartlyexplainedtheincreaseofsunshinehourin1960sandthedecreasein1970s(Fig.5.17).Downwardsolarradiationfluxhadbeenontherisefrom1981–1990to1991–2000,andtherelativehumidityinSouthwesternChinaexcludingHengduanMountaindeceased,whichwassametotheobservationdatafromgroundstationsandmaypartlyexplainedtheincreaseofsunshinehoursafter1990(Fig.5.17).5.3.5CorrelationwithSunshineHourandAltitudeAsaboveanalysismentioned,in1961–2008,thestationswithawidermarginofdecreaseinsunshinehourweremainlydistributedinlowaltitudeare,reflectedfromthedecreaseofsunshinehouralongwiththeriseofaltitude(Fig.5.18).Exceptfor 1645SpatialandTemporalVariationofSunshineHours…%6.949520.182915.104331.4615Summer−−−−50%(50%)91(46%)71%(44%)90%(68%)12.4317.056243.6891217.1948Wintermonsoon−−−−50%(50%)66%(20%)59%(24%)85%(53%)0.29954.237080.495094.93283monsoon−−−−50%(50%)74%(23%)41%(21%)70%(25%)20087.389713.584611.407123.2995–−−−−50%(0%)94%(43%)74%(41%)90%(65%)4.42856.225034.8511611.8654−−−−50%(50%)80%(23%)71%(26%)88%(45%)7.61343.137041.410868.29636−−−−50%(50%)57%(23%)62%(12%)83%(38%)19.35732.234620.516550.62490.2−−0.28−−0.1250%(50%)86%0.46(60%)62%(44%)0.0288%(73%)0.230.29cantdecreasingtrendfi2NumberAnnualWinter35Spring40SummerAutumn-fiCorrelationcoefcientwithaltitudeSummitValleyIntermountainFlatSummit34ValleyIntermountainFlatTherelationshipbetweentrendsinsunshinehoursandaltitudeortopographyduring1961Table5.9TrendsPercentwithdecreasingstationsValuesinbracesisthepercentageofstationswithsigni 5.3DrivingMechanismforSunshineHours165thesummerandmonsoon,thesunshinehourdidnothaveasignificantlystatisticalrelationshipwiththealtitude,whichsuggestedthattherewasnoobviousaltitudedependenceinsunshinehourofstudiedarea(Table5.9).Intermsofterraininfluence,flatstationhadthewidestmarginofdecreaseinsunshinehour,inturnfollowedbyvalleystation,intermontanestationandsummitstation.Thespring,summer,autumnandsummermonsoonsunshinehouralsohadsimilarfeatures.Andthemagnitudeofdecreaseinsummitstationduringwinterandwintermon-soonperiodwasapparentlygreaterthaninvalleyandintermontanestationbutlessthaninflatstation(Table5.9).Thepercentageofstationswithsignificantdecreasetrendalsoshowedasamechangethatitdeclinedfromflatstationtosummitstationinturnduringtheannual,springandwintermonsoonperiodanditdeclinedfromvalley,flat,intermontaneandsummitstationinturnduringsummer,autumnandsummerperiod(Table5.9).Onthewhole,themaximummarginofdecreaseoccurredinfaultstation,andtheminimumoccurredinsummitstations,whichmayberelatedtowindspeedbecausegenerallythewindspeedinsummitstationwasstrongerthanothertypesofstations.5.4SummaryThischapterfocusesontheanalysisofthetemporalandspatialvariationaswellastheinfluencingfactorsofsunshinehoursinSouthwesternChinain1961–2008.Theresultscanbeshowedasfollowing:(1)Itisveryobviousthatthesunshinehourschangesindifferentstages.Theannualmeansunshinehourwas1894hin1961–2008.Thelargervaluesofannualmeansunshinehoursweremainlydistributedinthehighaltitudeareas,suchasXizangPlateau,HengduanMountainandYunnanPlateau,whilethelowervalueswereinthelowaltitudearea,suchasGuizhouPlateauandSichuan.Theannualmeansunshinehoursharplydecreasedattherateof31.9h/10ain1961–2008,andtheinterannualchangeswereperformedbytheincreaseof1960s,thecontinuousdecreaseduring1970–1990andtheriseafterward.Theseasonalsunshinehoursalsohadadropbefore1990,thengrewupapparently,andthedeclinetrendisremarkableinsummerandsummermonsoonperiod.Thedecreasingmagnitudeofsunshinehourin1961–1990wasgreaterthanthatofentirestudiedperiod,whilethesunshinehourwasonasignificantrisein1991–2008exceptforinspring.(2)Thesunshinehourschangeismoresignificantinlowaltitudearea.Thesunshinehourofabout59%ofstationsinthestudiedstationsdecreasedsignificantlyin1961–2008whichweremainlydistributedinlowaltitudearea,especiallyinGuizhouPlateauandSichuanBasin.Whereasmoststationsinhighaltitudeareasshowedaslightdecreasingorincreasingtrend.Thestationswithadeclineweremainlydistributedinlowaltitudeareafrom1961to1990,whilethestationshowingaincreasingtrendwerelocatedinhighaltitude 1665SpatialandTemporalVariationofSunshineHours…areas.Therewereabout61%ofthestationsshowingarisingstationsinsunshinehourfrom1991to2008whichwereprimarilysituatedinlowaltitudearea.Differentfromthetemperatureandprecipitation,thesunshinehourschangesinthestudiedareadidnotrepresentaobviouscorrelationwithalti-tudeyet.Intermsoftheinfluenceofterrain,thewidestmarginofdecreaseoccurredinflatstations,andthenexttwowerevalleyandintermountainstation.Theleastmagnitudeappearedinsummitstations.(3)Thewindspeedandhumidityarethemaininfluencingfactorsofsunshinehoursinthestudiedareas.Exceptforinautumn,thewindspeedhadasig-nificantcorrelationwithsunshinehourschangein1969–2008,andtheyhadsamechangingtrend.Themagnitudeofdecreaseofsunshinehourin1969–2000wasapparentlygreaterthanin2001–2008,andthespatialdistri-butionpatternofthemweresimilartothatofwindspeedduringasameperiod.Inadditiontothespringandautumn,thesunshinehoursofstationswherethewindspeedwaslessthan1.5m/sdecreasedmuchmoresharplythanthatofstationswherethewindspeedwasmorethan1.5m/s,andthepercentageofformerstationswasgreaterthanthelatterones.Thehumiditywastheotherinfluencingfactorofsunshinehourchanges.Theoppositechangingtrendtosunshinehourwasshowedbyhumidityin1961–2008,andtheannualandseasonalchangeshadasignificantcorrelationwithsunshinehoursbecausethewatervaporintheaircouldweakenthesolarradiationbyabsorbing,scatteringandreflectingetc.Inaddition,thesunshinehourschangesalsohadaapparentcorrelationwiththechangeofdownwardsolarradiationflux,cloudwatercontent,areaofcloudcoverandprecipitation.(4)Thereislittlecorrelationbetweenacceleratedurbanizationprocessandsun-shinehours.Thechangingmagnitudeandpercentageofurbanstationswithadroppingtrendweremuchgreaterthanruralstationsin1961–2008,andtheincreasemagnitudesofannual,spring,autumn,winterandwintermonsoonsunshinehoursinurbanstationsweregreaterthanruralstations.However,thesunshinehourchangedidnotshowareversetrendtoacceleratedurbanizationprocess.Therewasnotreversetrendbetweensunshinehourandtheincreaseofaerosolconcentrationcausedbyenergyconsumption.Theinfluenceofaerosolconcentrationonsunshinehourinwinterisgenerallygreaterthaninsummer.Eitherinurbanorruralstations,thesummersunshinehourdecreasedmostsharplyin1961–2008,andonlythechangingmagnitudeofsunshinehoursinsummerwasnegativeduring1991–2008.ThedecreasingmagnitudeofsunshinehourinGuiyangandKunmingweremaximumintheirprovince.WhilethesunshinehourinKunmingincreasedin1991–2008,andobviously,thedecreasingmagnitudeinGuiyangwaslessthan1961–1990.Furtheranalysisfoundthattherootcauseofdifferencesbetweenurbanandruralstationsinsunshinehoursisthattheurbanstationsaremainlylocatedinlowaltitudeareas,suchasGuizhouPlateauandSichuanBasinwherethedecreasingmagnitudeofsunshinehourwasmaximumin1961–2008andtheincreasingmagnitudewasmoresignificantin1991–2008. 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Chapter6SpatialandTemporalVariationofWindSpeedinSouthwesternChina6.1TemporalVariationofWindSpeed6.1.1TheMeanWindSpeedTheannualmeanwindspeedinSouthwesternChinawas1.75m/sin1969–2008.Theannualmeanmaximumwindspeedwas4.26m/soccurredinBangeofTibetAutonomousRegion,andtheminimumwindspeedwas0.54m/soccurredinWanxianofSichuanProvince.Theseasonalmeanwindspeedwasgreatestinspring(2.15m/s)followedbywinter(1.78m/s),summer(1.61m/s)andautumn(1.47m/s)inturn.Theminimumwindspeedinspring,summer,autumnandwinterwererespectively0.69,0.59,0.35and0.35m/s,andthemaximumwindspeedinturnwere4.80,3.96,3.71and5.00m/s.Theannual,maximumandminimumwindspeedinsummerandwintermonsoonperiodwere1.80,0.55,3.61and1.51,0.59,2.87m/s.WestwindcirculationisakeyonetoinfluencetheclimatechangeinwintermonsooninSouthwesternChina,sothehighvalueofwindspeedinstudiedareaprimarilyappearedinwinterhalfyear.AsshowninFig.6.1,thestationwiththeannualmeanmaximumwindspeedweremainlydistributedinXizangPlateau,HengduanMountainandthecentralofYunnan–GuizhouPlateau.WhilethewindspeedofmoststationsintheeastandwestofYunnan–GuizhouPlateauandSichuanBasinwasweaker.Theseasonalmeanwindspeedalsohadasamedis-tributionpattern.Overall,annualmeanwindspeedweakenedfromwesttoeast,whichreflectingtheinfluenceofterrain.TheannualmeanwindspeedofXizangPlateau–HengduanMountainwas2.15m/s,whichobviouslygreaterthanthemeanofSouthwesternChinaandothertworegions.Itsmeansinspring,summer,autumn,winter,summermonsoonandwintermonsoonwererespectively2.67,1.91,1.78,2.2,2.32,and1.97m/s,whichallmorethanthecorrespondingvaluesinthestudiedarea.Theannualmeanwindspeedwas1.66m/s,andthemeansinspring,summer,autumn,winter,summermonsoonandwintermonsoonwererespectively2.01,1.5,1.37,1.73,1.8and1.51m/s,whichlowerthanthatofXizangPlateau–Hengduan©Springer-VerlagBerlinHeidelberg2015169Z.Li,StudyonClimateChangeinSouthwesternChina,SpringerTheses,DOI10.1007/978-3-662-44742-0_6 1706SpatialandTemporalVariationofWindSpeed…Fig.6.1Spatialdistributionofannualmeanwindspeedduring1969–2008,aannualwindspeed,bwinterwindspeed,cspringwindspeed,dsummerwindspeed,eautumnwindspeed,fWMPwindspeed,gSMPwindspeed 6.1TemporalVariationofWindSpeed171Mountain,butgreaterthanthatofSichuanBasin.Theannualandseasonalmean,maximumandminimumwindspeedallwerethesmallestamongthesethreeregions.Thesedifferencesreflectedagaintheinfluenceoftheterrainandaltitudeonannualmeanwindspeed.6.1.2TheInterannualVariationofWindSpeedTheannualmeanwindspeedofstudiedareasignificantlydecreasedattherateof0.24m/s/10ain1969–2008,andthedecreasingrate(0.37m/s/10a)in1969–2000wasremarkablygreaterthanthatin1969–2008,furthermorethewindspeedincreasedapparentlyattherateof0.55m/s/10ain2001–2008(Fig.6.2).In1969–1990,theannualmeanwindspeedinChinahadasignificantdropattherateof−0.25m/s/10aanddecreaseddrasticallyto−0.06m/s/10a,whichwassimilartothechangetrendofSouthwesternChina(Gaoetal.2010).FromtheresultsofcomparisoninTable6.2,thedecreasingmagnitudeofstudiedareainwindspeedwasgreaterthanthemeanlevelofChinaandotherregions,andthechangingtrendinspring,summer,autumn,winter,summermonsoonandwintermonsoonweresimilartotheannualtrendin1969–2008(Fig.6.2),correspondingchangetrendsineveryseasonwere−0.28,−0.16,−0.14,−0.22,−0.26and−0.18m/s/10a.Thechangingmagnitudeinwindspeedrespectivelywere−0.35,−0.26,−0.30,−0.38,−0.39and−0.29m/s/10ain1969–2000,whichallweregreaterthanthedecreasingmagnitudeinthewholestudiedarea.In2001–2008,theseasonalvariationtrendsinwindspeedwere0.13,0.13,0.13,0.82,0.33and0.74m/s/10a,amongwhichonlyspringhadnotpassedthesignificancetest(Table6.1).Themaximumdecreaseinstudiedareahappenedinwinterandspring,whilethemaximumoccurredinautumn,moreover,theincreasingmagnitudeinsummerwasthemaximumsince2001.TheseasonaldecreaseinSouthwesternChinawasapparentlygreaterthaninChinaandNorthernChina,butlessthanNortheasternChinaandQinghai-XizangPlateau(Table6.2).Inshort,theannualandseasonalwindspeedin1969–2008displayedanevidentlydecreaseinstudiedarea,butasharpriseturnedupafter2000.Thischangemeanedthattheincreaseofwindspeedalsoneededtobeverifiedinfurtherobservationdata.AsshowninTable6.1,althoughtheannualmeanwindspeedofthreesub-regionsduring1969–2008showedadeclinetrend,thereweresomedifferencesinthechangingtrends.In1960s,thewindspeedinXizangPlateau–HengduanMountainincreasedandhadasignificantdropin1970–2000,thendisplayedanrisingtrend.WhilethewindspeedinYunnan–GuizhouPlateauandSichuanBasincontinuedtodecreasebefore2000andfluctuatedtoincreaseafterward.TheannualandseasonaldecreasemagnitudeinwindspeedofXizangPlateau–HengduanMountainsucceededinpassingthesignificancetestin1969–2008andapparentlygreaterthanthatofYunnan–GuizhouPlateauandSichuanBasin.ThedroppingmagnitudeofSichuanBasininsummerandautumnwasreallysmallandhadnotpassedthesignificancetest.Inaddition,thewindspeedofYunnan–Guizhou 1726SpatialandTemporalVariationofWindSpeed…Fig.6.2AnnualandseasonalvariationsofwindspeedinSouthwesternChina.ReprintedbypermissionfromMacmillanPublishersLtd:Yangetal.(2012).Copyright(2012),aannual,bwinter,cspring,dsummer,eautumn,fwintermonsoonperiod,gwintermonsoonperiod 6.1TemporalVariationofWindSpeed1730.450.530.110.320.040.170.75−−−−−−0.460.540.20.460.150.310.02−−−−−−0.40.510.150.420.140.31−−−−−−0.390.530.070.310.17−−−−−0.420.490.110.310.0060.110.770.0080.680.29−−−−−−0.50.470.220.390.20.310.09−−−−−−−0.430.510.890.160.40.450.940.131.140.270.420.381.0210.940.820.77−−−−−−200820002008200820002008200820002008cantatthe5%levelaresetinbold–––––––––fiMaximumMinimumMaximum0.76Minimum4.26Maximum0.880.54Minimum4.83.05Regionaltrend0.890.640.633.9619693.14Annual3.0920010.610.590.76Spring2.793.7219693.9920010.64Summer0.350.592.845.012.791969Autumn0.6920010.350.45Winter4.893.412.81Wintermonsoon0.450.53.33.57Summermonsoon0.820.553.843.61Annualmeanwindspeed(m/s)andregionaltrends(m/s/10a)inthreesub-regionsofSouthwesternChinaTable6.1Sub-regionXPHMMeanwindspeedMeanAnnualSBSpringYGPSummerMean2.15AutumnMeanWinterXPHM2.67Wintermonsoon1.271.911969SBSummermonsoon1.491.661.78YGP1.2919692.012.2Valuesfortrendssigni1.519691.122.321.161.371.26 1746SpatialandTemporalVariationofWindSpeed…Table6.2WindspeedtrendsinChinaanditsregions(m/s/10a)PeriodAnnualSpringSummerAutumnWinterSourcesHeilongjiang1961–2004−0.31−0.40−0.23−0.30−0.32Zhouetal.–Chongqing1961–2007−0.04Lietal.(2010)Tibetan1980–2005−0.24−0.29−0.24−0.19−0.23Youetal.Plateau(2010)NorthChina1951–2006−0.16−0.19−0.10−0.15−0.22Liuetal.Plain(2009a,b)Northeastern1961–2000−0.23−0.33−0.16−0.18−0.24YangChinaChina1969–2005−0.18−0.21−0.15−0.19Guoetal.(2010)Plateauhadweakerchangesinaboveseasons.Exceptthatthedecreasingmagni-tudeofYunnan–GuizhouPlateauinsummerfailedtopassthesignificancetest,theremarkableincreasingmagnitudeinthesethreeregionshadpassedthesignificancetestcomparedwiththatof1969–2000.Asthewhole,thedroppingmagnitudeofXizangPlateau–HengduanMountainwasgreatestandtheSichuanBasinfollowed.In2001–2008,inadditiontoafaintdeclinesinspringandwintermonsoonwindspeedofYunnan–GuizhouPlateau,othersallexhibitedasignificantincrease,andamongthem,theincreasingmagnitudeinsummerandautumnweremaximum.TherisingmagnitudeofSichuanBasininannual,winterandwintermonsoonperiodbecamewider.Inotherseasons,theincreasingmagnitudeofXizangPlateau–HengduanMountainwasgreatestandthatofYunnan–GuizhouPlateauwasleast(Table6.1).Inconclusion,theincreasinganddecreasingmagnitudeofwindspeedinXizangPlateau–HengduanMountainweremaximum;theincreasingmagnitudeinSichuanBasinwasgreaterbutthedecreasingmagnitudewasless;windspeedinYunnan–GuizhouPlateauhadaslightchangeandhighstability.6.2SpatialVariationofWindSpeed6.2.1TheSpatialDistributionoftheWindSpeedVariationBetween1969–2008and1969–2000Theannualmeanwindspeedofabout77%ofthe110stationsin1969–2008displayedadecreasingtrend,andthestationswithsignificantdecreasetrendaccountedfor66%.ExcludingsomestationswithanincreasingwindspeedinthewestofYunnanPlateau,GuizhouPlateauandSichuanBasin,severalofwhichwerecharacterizedbyasignificantincrease,moststationswithawidermarginofdecreaseandhavingpassedthesignificancetestweremainlydistributedinXizangPlateau,HengduanMountainandYunnanPlateau(Fig.6.3).In1969–2000,about 6.2SpatialVariationofWindSpeed175Fig.6.3Spatialdistributionofvariationaltrendsinwindspeedduring1969–2008.ReprintedfromTheLancet:Yangetal.(2012).Copyright(2012),withpermissionfromElsevier,aannual,bwinter,cspring,dsummer,eautumn,fwintermonsoonperiod,gsummermonsoonperiod 1766SpatialandTemporalVariationofWindSpeed…82%ofthestationsshowedadroppingtrendinwindspeedandabout69%ofthestationssignificantlyreduced.TheywereXizangPlateau,HengduanMountain,YunnanPlateau,thewestofGuizhouPlateauandtheeastofSichuanBasin,whileafewstationsinthesouthwestedgeofYunnanPlateau,thecentralofGuizhouPlateauandSichuanBasinrevealedauptowardtrend(Fig.6.4).Andthestationpassingthesignificancetestaccountedfor67%.InadditiontoafewstationsinYunnan–GuizhouPlateauandSichuanBasin,thestationswithawidermarginofsignificantdecreasewerelocatedinXizangPlateauandHengduanMountain,whereasthestationsatlowaltitudehadalessdrop(Fig.6.3).Therewere95stationsdisplayingadowntrendfrom1969to2000and69stationshadpassedthesignificancetest.Amongthem,thestationswiththesignificantdeclinetrendweresituatedinXizangPlateau,HengduanMountainandYunnanPlateau,whilethemoststationsinGuizhouPlateauandSichuanBasinexhibitedanon-significantdecreasingtrendandsomestationshadaincreasingtrend(Fig.6.4).Theautumnwindspeedreducedinabout70%ofstationsduring1969–2008,butthedecreasingmagnitudeofjust48%ofstationslocatedintheeasternXizangPlateauandHengduanMountainhadpassedthesignificancetest.WhilethemoststationsinYunnan–GuizhouPlateauandSichuanBasinhadanincreaseornon-significantdecrease(Fig.6.3).From1969to2000,therewereabout78%of110stationsselecteddisplayingadecrease,butjust59%ofstationsdeclinedsignificantlywhichweremainlydistributedinXizangPlateau,HengduanMountainandYunnanPlateau.Thestationswithnon-significantdecreaseorincreasewereprimarilyintheedgeofYunnanPlateau,GuizhouPlateauandSichuan(Fig.6.4).Therewereabout76%ofstationsexhibitingadroppingwindspeedinwinterduring1969–2008,whilejust57%ofstationslocatedinXizangPlateau–HengduanMountaindeclinedsignificantly.ThemajorityofstationsinYunnan–GuizhouPlateauandSichuanBasinrevealedanon-significantdecreaseorincrease(Fig.6.3).Thewindspeedofapproximately86%of110stationswasonthedeclinedin1969–2000and73%ofstationsshowedasignificantdecreasewhichweredistributedinXizangPlateau,HengduanMountainandYunnanPlateau,whilethenon-significantdeclineorrisewasdisplayedinsomestationsofGuizhouPlateauandSichuanBasin(Fig.6.4).Inspringsof1969–2008,approximately84%ofthestationsreducedinwindspeed.Inwintermonsoonperiodof1969–2008,about80%ofthestationsdroppedinwindspeedandthedecreasingmagnitudeof65%ofstationswhichweresituatedinhighaltitudeareas,suchasXizangPlateau,HengduanMountainandYunnanPlateauhadpassedthesignificancetest.WhereasthewindspeedofafewstationsinthesouthwestedgeofYunnanPlateau,GuizhouPlateauandthecentralofSichuanhadarise.Thisdistributionpatternreflectedthesignificantinfluenceofterrain(Fig.6.3).About87%ofthestationsinXizangPlateau,HengduanMountainandYunnanPlateaushowedareducingtrendfrom1969to2000,amongthem,therewere76%ofstationssignificantlyreducing.Whilethestationsshowingnon-significantdecreaseweredistributedinGuizhouPlateauandSichuanBasin(Fig.6.4).Inthesummermonsoonperiodof1969–2008,thepercentageofstationshavingadowntrendintheannualmeanwindspeedwas71%whichweremainly 6.2SpatialVariationofWindSpeed177Fig.6.4Spatialdistributionofvariationaltrendsinwindspeedduring1969–2000,aannual,bwinter,cspring,dsummer,eautumn,fwintermonsoonperoid,gsummermonsoonperiod 1786SpatialandTemporalVariationofWindSpeed…locatedinXizangPlateau–HengduanMountainand56%ofthemhadpassedthesignificancetest,whilethestationsinYunnanPlateau,GuizhouPlateauandSichuanBasinincreasedandaccountedfor29%ofallstationsselected(Fig.6.3).In1969–2000,73%ofallstationsinXizangPlateau,HengduanMountainandYunnanPlateauhadadroppingwindspeedandthestationswherethedecreasingmagnitudepassedthesignificancetestaccountedforabout65%.Thereinto,theincreasingtrendinGuizhouPlateauwasmostremarkable(Fig.6.4).Onthewhole,thestationswherethewindspeeddeclinedin1969–2008and1969–2000weremainlydistributedinhighaltitudearea,andinlatterperiodthereweremorestationsshowingasignificantdecrease.Inaddition,thedecreasingmagnitudeexhibitedareducinglawfromwesttoeast,reflectingtheimpactofterrain.6.2.2SpatialDistributionofWindSpeedVariationDuring2001–2008theannualmeanwindspeedreducedinthestationsaccountingfor35%ofallstationsandlocatedinXizangPlateauandGuizhouPlateau.ThestationswithawidermarginofincreaseweremainlylocatedinHengduanMountain,YunnanPlateauandthewesternSichuanBasin(Fig.6.5).About59%ofthestationsinspringwindspeedincreasedandasignificantincreaseoccurredinthestationsaccountingfor42%ofallstationsinHengduanMountain,YunnanPlateauandSichuanBasin,whileseveralstationsinXizangPlateau,thecentralofHengduanMountainandGuizhouPlateaurevealedadecreasingtrend,amongthemthereweremoststationsdeclinedsignificantly(Fig.6.5).In2001–2008,thesum-merwindspeedinabout67%ofthestationsinthestudiedareawasontheriseandtherewere55%ofthestationsincreasedsignificantlywhichweremainlydistri-butioninHengduanMountain,YunnanPlateauandthewesternSichuanBasin,whiletheseveralstationsintheeastofXizangPlateau,GuizhouPlateauandtheeastofSichuanBasindecreasedsignificantly(Fig.6.5).Theautumnwindspeedincreasehappenedinthestationsaccountingfor66%of110stationsselectedandthe56%ofthestationspassedthesignificancetestwhichweremainlydistributedinYunnanPlateau,HengduanMountainandthewesternSichuanBasin.However,themoststationsinGuizhouPlateauandtheeastofXizangPlateaustillshowedasignificantdecreasetendency(Fig.6.5).Thewindspeedincreasesappearedinabout65%ofthestations,and51%ofthestationsincreasesignificantly.ThesestationsweredistributedinHengduanMountain,YunnanPlateauandSichuanBasin,whileanumberofstationsinXizangPlateauandGuizhouPlateauwereonthedecline(Fig.6.5).About63%ofthestationsinwintermonsoonwindspeedincreased,and51%ofstationsincreasedsignificantly,thesestationsaremainlylocatedinHengduanMountain,YunnanPlateauandSichuanBasin,whileadecreasingtrendstillappearedinthestationsintheeasternXizangPlateau,thesoutheasternHengduanMountainandsoutheasternYunnanPlateau(Fig.6.5).About67%ofstationsincreasedinsummerwindspeedduring2001–2008andthedramaticalincreasein58%ofthestationshadpassthesignificancetest. 6.2SpatialVariationofWindSpeed179Fig.6.5Spatialdistributionofvariationaltrendsinwindspeedduring2001–2008,aannual,bwinter,cspring,dsummer,eautumn,fwintermonsoonperoid,gsummermonsoonperiod 1806SpatialandTemporalVariationofWindSpeed…ThesestationsweremainlyinotherregionsexceptfortheeastofXizangPlateauandGuizhouPlateau(Fig.6.5).Allinall,in2001–2008,thewindspeedperformingaincreasingtrendmostlyweredistributedinYunnanPlateau,HengduanMountainandSichuanBasin.AndthestationswithadecreasingwindspeedwerelocatedinXizangPlateauandGuizhouPlateau.6.3DrivingMechanismforWindSpeed6.3.1CorrelationwithWindSpeedandLarge-ScaleAtmosphericCirculationInordertoexploretheinfluenceofatmosphericcirculationonwindspeed,thisstudymadeananalysisonthevariationsofmeridionalandzonalwindthroughtwoperiods.The2000yearwasthedividebetweenthem.Thisstudyalsodrewthedifferencefigureofmeridionalandzonalwindbetween1986–2000and1969–1985at500hPa.Thevariationwasrevealedthroughlatterperiodminustheformerperiod.Andtheregionrangeselectedwas20°N–40°Nand75°E–115°E.Moreapparently,inadditiontothewesternXizangPlateau,themeridionalwindhadbeenshowingadowntowardtrendfrom1969–1985to1986–2000instudiedareaandthezonalwindhadawidermarginofdecreaseinlatterperiod,suggestingthattheweakeningofwindspeedofwestwindcirculationandmonsooncirculationcouldbethemainreasonofthereductionofwindspeedinstudiedareabefore2000(Fig.6.6).TheresearchesresultsofDashetal.(2008)andWu(2005)alsocon-firmedthattheIndianmonsoonwasinanunstablestateandperformedadecreasingtrendinrecentyear.Withthepurposeoffurtheranalysisonthecorrelationwiththevariationofcirculationsystemandtheincreasingofwindspeedin2001–2008,thisstudydrewthedifferencefigureofmeridionalandzonalwindbetween1991–2000and2001–2008at500hPa.Thevariationwasrevealedthroughlatterperiodminustheformerperiod.AsshowninFig.6.7,overall,themeridionalwindinSouth-westernChinaexhibitedaapparentreducefrom1991–2000to2001–2008,par-ticularlyinXizangPlateauthedecreasingmagnitudewasgreatest.WhilethewindspeedinGuizhouPlateauandSichuanBasinhadaupwardtendency.ExceptingforYunnanPlateau,thezonalwindinstudiedareawasontheobviousrise.AboveresultsindicatedthatthestrengtheningofzonalwindmightplayanimportantroleontheincreasingofwindspeedinSouthwesternChinasince2000.AndtheIPCC’sfourthassessmentreport(2007)alsoconfirmedtheapparentstrengtheningtrendinthewestwindcirculationofthenorthernhemisphere.Fromtheanalysisofseasonalvariationofmeridionalandzonalwindin1969–1985and1986–2000(Fig.6.8),itwasfoundthatthespringwindspeedofmeridionalandzonalwindinstudiedareawasstrongerinlatterperiodthaninformerperiod,whichdemonstratedthefaintincrease.Whilethewindspeedalsodeclinedsignificantlyinformerperiod.Thesummerandautumnzonalwindin1986–2000wasgreaterthanin1969–1985,andthemeridionalwindstrengthened 6.3DrivingMechanismforWindSpeed181Fig.6.6Differenceofthealtitudinalwindspeed(a)andthelongitudinalwindspeed(b)at500hPabetween1986–2000and1969–1985inXizangPlateaubutweakenedinotherregions.Thewinterzonalwindchangedweakerbyalargemargininlatterperiod,whichsuggestedtheweakeningofcirculationsystem.Theseresultsindicatedthatfrom1969–1985to1986–2000,thewindspeedinotherseasonshadaslightcorrelationwiththeweakeningofmeridionalandzonalwindexceptforinspringandalsoverifiedthatthecommonimpactofthevariation 1826SpatialandTemporalVariationofWindSpeed…Fig.6.7Differenceofthealtitudinalwindspeed(a)andthelongitudinalwindspeed(b)at500hPabetween2001–2008and1991–2000ofatmosphericcirculationsystemonthechangeofwindspeed.From1991–2000to2000–1991,thezonalwindinspringinthewholestudiedareahadanobviousdecreasingtrendandthedecreasingmagnitudewaswiderathighaltitudeareawherethemeridionalwindalsoweakenedapparentlyexceptforYunnanPlateauandGuizhouPlateau.Itmaybepartlyexplainedtherelativelyweakgrowthinthespringwindspeed.Thesummerzonalwindspeedreducedslightlyinlatterperiod, 6.3DrivingMechanismforWindSpeed183Fig.6.8Differenceoftheseasonalaltitudinalwindspeed(a–d)andtheseasonallongitudinalwindspeed(e–h)at500hPabetween1986–2000and1969–1985fromspringtowinterwhilethemeridionalwindhadarisingtrendinmostregionsinadditiontothewestareasofXizangPlateau,whichreflectedthattheincreasingofmeridionalwindwasoneofpossiblereasonsofstrengtheningofwindspeed.Throughthecomparisonofthesetwoperiods,itwasrevealedthatthezonalwindspeedofstudiedareain 1846SpatialandTemporalVariationofWindSpeed…Fig.6.9Differenceoftheseasonalaltitudinalwindspeed(a–d)andtheseasonallongitudinalwindspeed(e–h)at500hPabetween2001–2008and1991–2000fromspringtowinterautumnstrengthenedbyawidermargininlatterperiodthaninformerperiod,andshowedaincreasingtrendinotherregionsexceptthatadowntrendwasexhibitedinXizangPlateau,whichsuggestedthattheinfluenceofthestrengtheningofautumnzonalwindonthewindspeedvariation.Thewinterzonalwinddeclined 6.3DrivingMechanismforWindSpeed185significantlyinXizangPlateauandthenorthernSichuanBasin,whileawidermarginofincreaseappearedinthesouthpartofstudiedarea,especiallyinYun-nan–GuizhouPlateau.Furthermore,themeridionalwindalsoshowedasimilarchangingfeature.Itpartlyexplainedtheincreaseofthewinterwindspeed(Fig.6.9).Inrecentyears,alargenumberofstudieshadconfirmedthattheweakeningofmonsooncirculationmadeasignificantcontributiontothereduceofwindspeedinChina.TheresearchofXuetal.(2006a,b)foundthattheweakeningeastAsianmonsoonswastheimportantreasonofthedecreaseofaveragesurfacewindspeedoverthepassed30years,andinEasternChinaanditsadjacentseaareaat850hPatheannualmeanwindspeedalsowascharacterizedbyadownwardtrend,reflectingtheabatingofeastAsianmonsoon(Xue2001).Inaddition,thelowerpressuredifferencebetweenlandandseaalsoconfirmedtheweakeningofthemonsooncirculationsysteminrecentyears(Guoetal.2003).Thiskindofevidencesalsoincludedtheloweringaveragewindspeedofnorth-southdirectioninCentralandEasternChinaat850and850hPa(Yuetal.2004)andtherisinggeopotentialheightofisobaricsurfaceat500hPa(HuangandYan1999).Moreover,thereweresimilarchangingtrendingeopotentialheightofisobaricsurfaceat850and500hPainEurasiaandwesternPacificin1961–2001(Wengetal.2004),implyingthecorrelationwiththeweak-eningintensityoftheeastAsianmonsoonandfactorsrelatedofinfluencingthelarge-scaleclimatechangesintheAsia–Pacificregion.Inadditiontoglobalwarmingwhichwasthemostobviousfactor,otherfactorsincludedthefrequencyofincreasingpositiveindexattheannularmodalofnorthernhemisphere(WallaceandThompson2001)andthemechanismchangeofclimateindecadal-scaleappearedinnorthernPacificnearly1976(WangandLi2004).ThestudyresultsofZhangetal.(2008a,b,c)suggestedthattheannualmeanwindspeedatupper,middleandlowertroposphericwerecharacterizedbythedeclinetrendfrom1980to2006inChina.Thesefactsindicatedagainthatthelarge-scaleatmosphericcirculationsystemfeaturingweak-eningmonsooncirculationwasoneoftheimportantfactorsresultinginthedecreaseofsurfacewindspeedinSouthwesternChina.Inadditiontothewestwindandmonsooncirculation,SouthwesternChinawasaffectedbyplateaumonsoontoo.Sothisstudyalsoanalyzedtheinfluenceofplateaumonsooninwindspeedvariation.PlateaumonsoonchangewasgenerallymeasuredbytheindexofQinghai-XizangPlateau,andreferredtotheaccumulativetotalvalueafterthattheheightvaluesateachlatticepointminusthepotentialat500mwithinthespecificarea.Thereweretwoindexes,thecalculationareaofoneindexAwas25–35°Nand80–100°E;theotherwas30–40°Nand75–105°E.ThisresearchadoptstheindexBofQinghai-XizangPlateau.AsshowninTable6.3,theannualandseasonalQinghai-XizangPlateauindexincreasedfrom1969to2008,andthemarginofincreaseinwinterwaswidest,upto7.38hPa/10awhichpassedthesignificancetest.Moreimportantly,theannualaveragewindspeedandtheplateauindexhadasignificantlynegativecorrelationandthecorrelationcoefficientwas0.56(P<0.0001).Theseasonalvariationalsoshowedasignificantlynegativecorrelation(Table6.3),especiallytheautumncorrelationcoefficientreached−0.67(P<0.05).ThusitwasprovedthatthestrengtheningQinghai-XizangPlateauindex 1866SpatialandTemporalVariationofWindSpeed…Table6.3VariationofTibetanmonsoonanditscorrelationwithwindspeed(hPa/10a)PeriodAnnualSpringSummerAutumnWinterWMPSMP1969–2008Trends(°C/a)4.282.772.824.167.385.233.24Correlation−0.56−0.32−0.49−0.67−0.55−0.4−0.62coefficients1969–2000Correlation−0.51−0.15−0.48−0.7−0.53−30−0.66coefficients2001–2008Correlation−0.37−0.5−0.57−0.29coefficientsValuesfortrendssignificantatthe5%levelaresetinboldhadsignificantinfluenceonthedecreaseofwindspeedinSouthwesternChina,becauseitaffectedthewindspeedonthegroundbychangingtheregionalatmo-sphericcirculationmode.Asisknowntoall,Qinghai-XizangPlateauaffectedtheglobalandregionalatmosphericcirculationsystembythestrongheatanddynamicaction,suchasthestrengthofwestwindandAsianmonsoon.Andtheremarkableincreaseofplateauindexhadanimpactonregionalmonsooncirculationandwestwindcirculation,thencausedthechangeofgroundwindspeed.Butthespecificmechanismofactionstillneededbestudiedfurther.6.3.2CorrelationwithWindSpeedandRegionalWarmingAnumberofstudies(Liuetal.2009a,b;Yan2002;Gadgil2007;Trenberthetal.2007)hadaffirmedthatthereducingofwindspeedinrecentdecadesinChinawasinfluencedbythecontinentalscaleclimatechange,especiallytheEurasiantem-peratureriseinrecentyears.Forexample,thehigherthegroundtemperatureinwintermightreducethesurfacepressure,thusweakenedthetemperatureandthepressuregradientbetweenthelandandtheadjacentsea,eventuallyreducedpres-suregradientforceandledtothedecreaseofthewindspeed(Xuetal.2006a,b).ThestudyofXuetal.alsothoughtthattheweakeningofwintermonsoonmainlywasrelativewiththewidermarginofwarminginNorthernChina,whiletheweakeningofsummermonsoonwasrelatedtotheslightcoolingofthecentralandsouthofChinaandthesignificantwarminginthesouthChinaseaandwestofnorthpacific,verifyingthesignificantinfluenceofthechangeinpressuregradientcausedbytheasymmetricvariationoftemperatureonthewindspeed.AsshowninTable6.4,generallyin1969–2008,theannualandseasonalmeantemperature,meanmaximumandminimumtemperaturesshowedsignificantwarmingtrend,andthemagnitudeofminimumtemperaturewaswidest.Moreimportantly,theannualmeanwindspeedhadanegativecorrelationwiththeannualmeantemperatureandmeanmaximumandminimumtemperatures,butthecorrelationwithmaximumtemperaturefailedinthesignificancetest(Table6.5).Inseasonalscale,theannualmeanwindspeedjusthadasignificantlynegativecorrelationwiththemeantem-peratureinautumnandwintermonsoonperiod,buthadnoobviouscorrelationwith 6.3DrivingMechanismforWindSpeed187Table6.4Variationoftemperatureduring1969–2008inSouthwesternChina(°C/10a)AnnualSpringSummerAutumnWinterWMPSMPTrendsMean0.410.240.230.340.250.320.28(°C/a)temperatureMaximum0.280.090.160.280.140.190.19temperatureMinimum0.490.350.40.370.360.410.41temperatureValuesfortrendssignificantatthe5%levelaresetinboldTable6.5TemperaturetrendsandtheircorrelationwithwindspeedinSouthwesternChinaRegionTemperatureAnnualSpringSummerAutumnWinterWMPSMPSouthernMean−0.4−0.220.03−0.33−0.26−0.3−0.15temperatureChinaMaximum−0.220.060.2−0.22−0.03−0.070.03temperatureMinimum−0.54−0.45−0.28−0.33−0.41−0.53−0.32temperatureXPHMMean−0.49−0.31−0.32−0.37−0.22−0.4−0.33temperatureSBMean0.090.180.470.03−0.080.050.27temperatureYGPMean−0.170.20.44−0.002−0.0010.030.32temperatureValuesfortrendssignificantatthe5%levelaresetinboldthemeantemperatureinsummer.Whilethenegativecorrelationwithotherseasonscouldnotpassthesignificancetest.Therewasasignificantlynegativecorrelationbetweenwindspeedandmeanminimumtemperatureandtherewasnoapparentcorrelationbetweenwindspeedandmeanmaximumtemperatureinadditiontoautumn.Itverifiedthattheclimatewarming,especiallytherisingofminimumtemperaturewasanotherkeyfactorleadingtothemarkeddecreaseofwindspeedinthestudiedarea,andthereversechangingtrendsbetweenwindspeedandtem-peraturealsosupportedthisconclusion.Horizontalpressuregradientforceisthedirectcauseandthepowerofairhorizontalmovement,whilethechangeofhorizontaltemperaturegradientisthemainfactorofchangeofhorizontalpressuregradient.Forexample,theasymmetricriseoftemperatureledtothedecreaseoftemperaturegradientintheregionallevel,thenresultedintheabatingofhorizontalpressuregradientforceandeventuallymaderegionalwindspeedreduce.ThestudyofZhangetal.(2008a,b,c)foundthatthereductionofthemeridionalthermalgradientinthemiddleandhighaltitudeareamadethemagnitudeofwarminginhighaltitudeareawiderthaninlowaltitudeareasince1980s,resultinginthedecreaseofwindspeed.ThestudyofKlink(1999)alsoconsideredthatthechangeinwindspeedcausedbythermaldifferencewasrelatedtothechangeofsurfacepressuregradientresultedfromgroundtemperaturegra-dient,especiallyinhighaltitudearea.Inordertoverifywhetherthereisdecreasein 1886SpatialandTemporalVariationofWindSpeed…zonaltemperaturegradient,threeregionswereselectedwiththelongituderangeof80°E–110°E:lowlatitudes(15°N–25°N),middle-latitude(45°N–35°N)andhighlatitudes(55°N–65°N).Thisstudycalculatethedifferencesofsurfacetemperatureandpressuregradientamonglow,mediumandhighlatitudesbyusingtheNCEP/NCARreanalysisdataonmonthlymeanairtemperatureandairpressure.AsshowninFig.6.10,in1969–2008,thetemperaturesinthreeregionsoflow,mediumandhighlatitudessignificantlywarmed,andthemagnitudewererespectively0.13°C/10a,0.24°C/10Fig.6.10Variationofsurfacetemperature(a–c)andpressure(d–f)inlower,middleandhigheraltitudeareasduring1969–2008.ReprintedfromTheLancet:Yangetal.(2012).Copyright(2012),withpermissionfromElsevierahighlatituderegions,bmiddlelatituderegions,clowlatituderegions,dhighlatituderegions,emiddlelatituderegions,flowlatituderegions 6.3DrivingMechanismforWindSpeed189aand0.50°C/10a,whichallpassedthesignificancetest.Obviously,themagnitudeofwarminginhighlatitudeswasgreatest.Theasymmetricwarmingindifferentlatitudeswouldreducethedifferencesofzonaltemperatureandleadtothedeclineoflatitudinaltemperaturegradients.Intermsofpressurechange,althoughthesurfacepressuresofthreelatitudeswereontheincrease,themagnitudeofairpressureriseinmiddlelatitudewasmaximumandthatinhighlatitudeswasminimum.Italsoshowedanasymmetricchange(Fig.6.10).Moreimportantly,underthebackgroundofasymmetricwarming,theannualmeanpressuregradientinlow–middlelatitudesareaandmiddle–highlatitudesregionpresentedadowntrendin1961–2008(Fig.6.11),whichwouldresultinthedecreaseofwindspeed.Therefore,theweakeningofpressuregradientbetweendifferentlatitudesisanimportantreasonofdecreaseofwindspeedunderthebackgroundofwarming.Theinfluenceoftemperatureonwindspeedchangealsoshowedobviousregionaldifferences.AsshowninTable6.5,theannualandseasonalwindspeedchangeinXizangPlateau–HengduanMountainhadsignificantlynegativecorrela-tionswiththetemperaturechangeexceptforthewinter,whilethewindspeedinYunnan–GuizhouPlateauandSichuanBasinshowedapositivecorrelationwiththetemperatureinsummerandsummermonsoonperiod.Theotherseasonalandannualtemperaturehadlowercorrelationwiththewindspeedwindchange,reflectingthemoresignificantinfluenceofwarmingonwindspeedinhighaltitudearea.Thisconfirmedagainthatthewindspeedchangecausedbythermaldifferencemainlyappearedinhighaltitudearea(Klink1999).Inaddition,thefurtheranalysisfoundthatthecorrelationcoefficientsofannualwindspeedandthemaximumandminimumtemperatureinXizangPlateau–HengduanMountainwere−0.65and−0.40,respectivelyandhadpassedthesignificancetest.ThecorrespondingvaluesintheSichuanBasinwere–0.04and0.19andinYunnan–GuizhouPlateauwere–0.34and0.06,reflectingthatthewarmingofminimumtemperaturehadamostinfluenceonreductionofwindspeedbecausetherisingmagnitudeandthewarmingtrendofminimumtemperatureweregreatest.Fromtheanalysis,itwassuggestedthatthechangingtrendsofminimumtemperatureinXizangPlateau–HengduanMountain,Yunnan–GuizhouPlateauandSichuanBasinin1969–2008wereFig.6.11Annualmeanpressuregradientinlow–middlelatitudes(a)areaandmiddle–highlatitudes(b)regionpresentedadowntrendin1961–2008 1906SpatialandTemporalVariationofWindSpeed…respectively0.52,0.51,and0.45/10a,andthemaximumtemperaturewere0.31,0.31,and0.22/10ain1969–2008.6.3.3CorrelationwithWindSpeedandSunshineHourTheannualmeansunshinehourinSouthwesternChinaperformedadecreasingtrendin1969–2008,andtheseasonalsunshinehourdeclinedsignificantlyinadditiontoautumn.Thesimilarchangingtrendwasshownbysunshinehourandwindspeed(Fig.5.9),andotherseasonhadasignificantlypositivecorrelationwiththewindspeedexceptforautumnandwinter(Table6.6),suggestingtheinteractionofsunshinehourandwindspeed.Becausetheheatingeffectofalongersunshinehourtoatmospherebecamestronger,thusacceleratedtheatmosphericmovementandformedafasterwindspeed,andviceversa.Thepreviousanalysisalsocon-firmedthatthesunshinehourisoneofinfluencingfactorsofwindspeedchange,indicatingtheinteractionandimpactbetweenthem.Theeffectofsunshinehourchangeonwindspeedalsoshowedacertainregionaldifference.Inadditiontowinter,theannualandseasonalchangeofwindspeedrevealedthesignificantlypositivecorrelationwithsunshinehourinXizangPlateau–HengduanMountain,whileinSichuanBasin,thesignificantlypositivecorrelationwasshowninotherseasonsexceptautumn.AndthepositivecorrelationwasshownonlyinsummerandautumninYunnan–GuizhouPlateau(Table6.6),suggestingthecommoninfluenceofsunshinehouronwindspeedchangeinstudiedareaandthesignificantimpactonhighaltitudeareas.WhiletheinfluenceofsunshinehouronlowaltitudearealikeYunnan–GuizhouPlateauandSichuanBasinmainlyappearedinwinterhalfyear.Inaddition,therewasalittleinfluenceofwintersunshinehourschangeonthewindspeedathighaltitudebecausethesunshinehourwaslongerinwinteranditschangewasrelativelystable.However,duetotheenlargementofsnowareainhighaltitudearea,thealbedodecreased,eventuallycausedthatthegroundnetradiationreducedandmadetheheatingeffecttoatmospheresubdue.Intheautumn,thesunshinehourchangehadalittleinfluenceonYunnan–GuizhouPlateauandSichuanBasinbecausetheautumnprecipitationwasrelativelyconcentratedandcloudcoverwaslarge,sothewindspeedmightbeinfluencedbytheintensityofmonsoon.Table6.6CorrelationbetweensolardurationandwindspeedinSouthwesternChinaRegionAnnualSpringSummerAutumnWinterWMPSMPSouthwesternChina0.460.40.530.140.280.470.52XPHM0.60.510.580.480.140.350.63SB0.540.440.560.110.370.610.43YGP0.50.570.260.180.450.430.26Valuesfortrendssignificantatthe5%levelaresetinbold 6.3DrivingMechanismforWindSpeed1916.3.4CorrelationwithWindSpeedandAltitudeThepreviousanalysisfoundthatthemeanwindspeedanditsvariationtrendshowedanapparentdroppingtrendfromwesttoeast,whichwasconfirmedbythechangeofannualandseasonalmeanwindspeedindifferentaltitudes(Fig.6.12).AsshowninFig.6.13,thechangingtrendsofboththeannualandseasonalwindspeedhadthenegativecorrelationwithaltitude,inotherwords,thedecreasingmagnitudewidenedwiththeriseofaltitude,verifyingthatthedecreaseofwindspeedmainoccurredinhighaltitudearea.Inordertofurtherunderstandtheinfluenceoftheterrain,theterrainof110observationstationswasdividedintofourtypes:summitstation,flatstation,intermountainstationandvalleystation.AsshowninTable6.7,thedecreasingmagnitudeofwindspeedreducedfromsummitstation,intermountainstation,flatstationandvalleystationinturnduring1969–2008.Theminimalreductionappearedinvalleystationandtheseasonalwindspeedalsoshowedasamechangingpattern.Theannualwindspeedinabout100%ofsummitstation,82%ofintermountainstation,63%offlatstationand65%ofvalleystationsdisplayedaremarkabledecrease.About65%ofinter-mountainstationsstrandedatabove1,500mandonly35%offaltstationswerelocatedinabove1,500m.Thedecreaseofwindspeedmainlyoccurredinhighaltitudearea,sotheintermountainstationsshowingthedowntrendweremorethanflatstations.Thedecreasingmagnitudewasleastbecauseofthehinderingeffectofvalleyterraintoairflowmovement.Thesefeaturesdemonstratedagainthatthedecreaseofwindspeedmainlyoccurredinhighaltitudeareaandalsosuggestedtheinfluenceofterraintypesonwindspeedchange.Fig.6.12ThevariationofAnnual4.5annualmeanwindspeedwithwinteraltitudeduring1969–20084.0SpringSummer3.5AutumnWMP3.0SMP2.5Windspeed(m/s)2.01.51.04500-50003500-40002500-30001500-2000500-1000Altituderank(m) 1926SpatialandTemporalVariationofWindSpeed…Fig.6.13ThecorrelationbetweenregionaltrendsofwindspeedandaltitudeTable6.7Meantrendsofwindspeedatdifferenttopographicalsites(m/s/10a)TerraintypesNumberAnnualSpringSummerAutumnWinterWMPSMPSummitstation2−0.2−0.24−0.15−0.16−0.26−0.24−0.16Intermountain34−0.18−0.24−0.14−0.13−0.18−0.21−0.15stationFlatstation40−0.16−0.18−0.09−0.01−0.16−0.17−0.01Valleystation34−0.007−0.009−0.007−0.005−0.06−0.007−0.0076.3.5ComparisonofWindSpeedBetweenUrbanandRuralStationsInaddition,numerousstudiesalsofoundthatinrecentyears,theacceleratedurbanizationisoneoftheinfluencefactorsofthedecreaseofwindspeed,becausealargenumberofurbanconstructionchangedthesurroundingenvironmentoftheurbanmeteorologicalstations,particularlytheblockresultedfromthistoatmo-sphericmovementwouldreducethegroundwindspeed,thusbringbiggererrortoobservationresults.ThestudyofKlinkconfirmedthatasmallermarginofchangesingroundsurfacestructurewouldcausethedecreaseofobservedwindspeed,for 6.3DrivingMechanismforWindSpeed193example,urbanization,airpollution,landuseandcoverchange.Inordertoanalyzetheeffect,110stationscouldbedividedintotwotypes:urbanstationandruralstations,andthedifferencesofchangingtrendwerecontrastivelyanalyzed.AsshowninTable6.8,in1969–2008,theannualandseasonalmean,maximumandminimumwindspeedofurbanstationsinstudiedareaweregreaterthanthatofruralstationbecausetheurbanstationsweremainlylocatedinlowaltitudearealikeYunnan–GuizhouPlateauandSichuanBasin.In1969–2008,thedecreasingtrendofannualandseasonalwindspeedbetweenurbanandruralstationhadpassedthesignificancetest,butthedecreasingmagnitudeinruralstationwasgreaterthaninurbanstationandthepercentageofstationswithsignificantdecreasewasmorethanthatofurbanstation,verifyingtheinfluenceofaltitudesbecausethestationswithsignificantdecreaseweremainlylocatedinthehighaltitudearea(Table6.9).Inaddition,althoughthepercentageofstationswithdecreaseandsignificantdecreaseinruralstationsweregreaterthaninurbanstationsin1969–2000(Table6.9).During2001–2008,theincreasingmagnitudeofannual,spring,autumn,summermonsoonandwintermonsoonperiodinruralstationsweregreaterthaninurbanstations.Theincreasingmagnitudeofurbanstationsinautumnandwinterweregreater,andmorestationswithincreasingtrendweredistributedinruralregion,buttheurbanstationsshowingsignificantincreasingtrendweremorethanruralstations(Table6.9).Theaboveanalysisindicatedthatthedifferenceinaltitudebetweenurbanandruralstationswasthemainreasonleadingtothedifferenceofchangingtrendinwindspeed.Table6.8Annualmeanwindspeed(m/s)andtrends(m/s/10a)inurbanandruralstationsinSouthwesternChinaWindspeedAnnualSpringSummerAutumnWinterWMPSMP(m/s)UrbanMean1.61.941.51.351.621.71.5stationMaximum0.540.640.590.450.450.510.57Minimum3.284.172.792.844.014.022.87RuralMean1.922.381.741.611.962.071.77stationMaximum0.560.740.590.350.350.450.59Minimum4.264.83.963.725.014.893.84Trend(m/s/10a)Urban1969–2008−0.25−0.31−0.1−0.14−0.25−0.29−0.15station1969–2000−0.43−0.41−0.26−0.35−0.42−0.44−0.322001–20080.420.130.540.30.670.340.45Rural1969–2008−0.29−0.32−0.23−0.21−0.26−0.29−0.26station1969–2000−0.38−0.34−0.27−0.34−0.38−0.38−0.332001–20080.70.230.110.770.60.370.97ReprintedfromTheLancet:Yangetal.(2012).Copyright(2012),withpermissionfromElsevierValuesfortrendssignificantatthe5%levelaresetinbold 1946SpatialandTemporalVariationofWindSpeed…Table6.9Percentageofstationswithnegativeorpositivetrendsofwindspeedinurbanandruralstations,SouthwesternChinaPeriodUrbanstationRuralstationUrbanstationRuralstationD(%)SD(%)D(%)SD(%)I(%)SI(%)I(%)SI(%)Annual1969–2008674887711969–2000796685732001–200860596960Spring1969–2008795987771969–2000906481622001–200860485835Summer1969–2008604088671969–2000745085732001–200866526960Autumn1969–2008554085631969–2000745283672001–200864596954Winter1969–2008674885691969–2000836790792001–200866536552WMP1969–2008745785731969–2000886787712001–200862536348SMP1969–2008554587711969–2000675779732001–200866606956Abbreviationsareasfollows:Disthepercentageofstationswithdecreasingtrend,andSDisthepercentageofstationswithsignificantdecreasingtrend;Iisthepercentageofstationswithincreasingtrend,andSIisthepercentageofstationswithsignificantincreasingtrend6.4SummaryThischapterfocusesontheanalysisonthespatialandtemporalvariationsofwindspeedaswellasitsinfluencingfactorsfrom1969to2008inSouthwesternChinabyusingdailywindspeedobservationdataof110stations.Theresultsindicatedasfollowing:(1)Thewindspeeddecreasedsignificantly,especiallyinhighaltitudearea.Themeanwindspeedwas1.75m/sin1969–2008,andthehighervaluesofannualandseasonalwindspeedaremainlydistributedinXizangPlateau,HengduanMountainandthecentralofYunnan–GuizhouPlateau,whilethewindspeedofmoststationsintheeastandwestofYunnan–GuizhouPlateauandSichuanBasinwasweaker.In1969–2008,theannualaveragewindspeedsignificantlyreducedattherateof0.24m/s/a.Thechangingtrendofwindspeedin1969–2000was−0.37m/s/10a,andthewindspeedstrengthenedapparently 6.4Summary195in2001–2008andthechangingtendencyofseasonalwindspeedwassimilartotheannualone.Thedecreasingmagnitudeofwindspeedin1969–2000werehigherthanthecorrespondingvaluesoftheentirestudiedperiod.About66%ofthestationsin1969–2008showedasignificantreduceinannualaveragewindspeed,andmorestationsdisplayedadecreasingtrendfrom1969to2000,whilethewindspeedofalmostmorethanhalfofstationsincresedsharplyin2001–2008.Onthewhole,thestationswithadecreasingwindspeedweresituatedinhighaltitudeareaandthechangingmagnitudeexhibitedadeclinetrendfromwesttoeast.In2001–2008,thestationswithincreasingtrendweremainlylocatedinHengduanMountain,YunnanPlateauandSichuanBasin,andthestationswithaweakeningwindspeedweredistributedinXizangPlateau,andGuizhouPlateau.(2)Theatmosphericcirculationisthemaininfluencingfactorofthewindspeedchangesinthestudiedarea.Themeridionalwindsshowedalowertrendfrom1969–1985to1985–2000instudiedareaexceptforthewestofXizangPlateau,andthedecreasingtrendofzonalwindinlatterperiodwasgreaterthaninformerperiod,suggestingthattheweakeningofwindspeedofwestwindcirculationandmonsooncirculationmightbethemaincauseofreduceinwinspeedbefore2000.From1991–2000to2000–2008,inadditiontotheYunnanPlateau,thesignificantincreaseofzonalwindindicatedthatthestrengtheningofzonalwindmightplayanimportantroleintheincreaseofwindspeedsince2000.Theremarkableinfluenceofatmosphericcirculationonwindspeedalsobeconfirmedbytheseasonalchangesofmeridionalandzonalwinds.In1969–2008,Qinghai-XizangPlateauindexdisplayedanuptrend,andtherewasasignificantlynegativecorrelationbetweenannualandseasonalwindspeedandplateauindex,reflectingtheapparenteffectofthestrengtheningofQing-hai-XizangPlateaumonsoononthedecreasingwindspeedinstudiedarea.(3)Theregionalclimatewarmingisanotherreasonofdecreasingwindspeed.Annualmeantemperatureandmeanminimumtemperatureshowedasignif-icantlynegativecorrelationwithannualmeanwindspeed.Inseasonalscale,thewindspeedjusthadasignificantnegativecorrelationwiththemeantemperatureandmeanminimumtemperatureinautumnandwintermonsoonperiod,reflectingthatthetemperaturerise,especiallythewidermarginofwarminginminimumtemperatureswasakeyfactorofweakeningofwindspeed.Furtheranalysisfoundthatin1969–2008,thewarmingmagnitudeofhighlatitudesareawasgreatest;theincreasingmagnitudeofairpressureinmiddlealtitudeareawasgreatestandtheincreasingmagnitudeofairpressureinhighaltitudeareawasleast.Inthecontextofthis,theannualmeanpressuregradientinthelow-middlealtitudeareasandthemiddle-highaltitudeareasreducedyearbyyear,indicatingthatthereductionofpressuregradientforcewasthemainreasonoftheweakeningofwindspeed.(4)Thesunshinehourandaltitudeetc.Alsohavesomeeffectonthewindspeedchanges.Inadditiontotheautumnandwinter,windspeedshowedasignif-icantlypositivecorrelationwithsunshinehour.Thesignificantlynegativecorrelationwithannualandseasonalwindspeedchangesandthealtitudes 1966SpatialandTemporalVariationofWindSpeed…affirmedtheelecationeffectofwindspeed.Thedecreasingmagnitudeofwindspeedreducedfromsummitstation,intermountainstation,flatstationandvalleystationinturnduring1969–2008.Thedecreasingmagnitudeofwindspeedinruralstationwasgreaterthaninurbanstationin1969–2008and1969–2000,andthepercentageofruralstationsperformingsignificantdecreasingtrendwasgreater.In2001–2008,theincreasingmagnitudeofwindspeedinannual,spring,autumn,summermonsoonandwintermonsoonperiodwasgreaterthaninurbanstation,andtheruralstationswithincreasingtendencyweremorethanurbanstations.Furtheranalysisfoundthatthedif-ferentaltitudesoftwotypesofstationswerethemainreasonofthesedifferences.ReferencesDash,S.K.,etal.(2008).ChangesinthecharacteristicsofraineventsinIndia.JournalofGeophysicalResearch,114,D10109.Gadgil,S.(2007).TheIndianmonsoon.PhysicsoftheMonsoonResonance,12,4–20.Gao,H.,etal.(2010).Changesinnear-surfacewindspeedinChina:1969–2005.InternationalJournalofClimatology.doi:10.1002/joc.2091.Guo,Q.Y.,etal.(2003).InterdecadalvariabilityofEast-AsiansummermonsoonanditsimpactontheclimateofChina.JournalofGeographicalSciences,58(4),569–576.(inChinese).Guo,Y.L.,etal.(2010).Spatialandtemporaldistributioncharacteristicofsunshinehoursanditsinfluencefactorsduring1965–2005inHebeiprovince.JournalofAridMeteorology,28(3),297–303.(inChinese).Huang,G.,&Yan,Z.(1999).TheEastAsiansummermonsooncirculationanomalyindexandtheinterannualvariationsoftheEastAsiansummermonsoon.ChineseScienceBulletin,44,1325–1329.Klink,K.(1999).TrendsinmeanmonthlymaximumandminimumsurfacewindspeedsinthecoterminousUnitedStates,1961to1990.ClimaticResearch,13,193–205.Li,Y.,etal.(2010).ThechangefeaturesofwindspeedinChongqingduring1961–2007.TransactionsofAtmosphericSciences,33(3),336–340.(inChinese).Liu,X.,etal.(2009a).ElevationdependencyofrecentandfutureminimumsurfaceairtemperaturetrendsintheTibetanPlateauanditssurroundings.GlobalandPlanetaryChange.doi:10.1016/j.gloplacha.2009.03.07.Liu,B.,etal.(2009b).CharacteristicsofclimatechangesinXinjiangfrom1960to2005.ClimaticandEnvironmentalResearch,14(4),414–426.(inChinese).Solomon,S.,etal.(Eds.).(2007).Intergovernmentalpanelonclimatechange(IPCC),summaryforpolicymakers,inclimatechange:Thephysicalsciencebasis.contributionofworkinggroupItothefourthassessmentreportoftheintergovernmentalpanelonclimatechange(pp.1–13).Cambridge:CambridgeUniversityPress.Trenberth,K.E.,etal.(2007).Observations:surfaceandatmosphericclimatechange.InS.Solomon(Ed.),Climatechange2007:Thephysicalsciencebasis,contributionofworkinggroupItothefourthassessmentreportoftheintergovernmentalpanelonclimatechange(pp.237–336).Cambridge:CambridgeUniversityPress.Wallace,J.M.,&Thompson,D.W.J.(2001).ThePacificcenterofactionoftheNorthernHemisphereannularmode:Realorartifact?JournalofClimate,14,1987–1991.Wang,B.,&Li,T.(2004).EastAsianmonsoonandENSOinteraction.InC.P.Chang(Ed.),EastAsianmonsoon(pp.177–212).Hackensack:WorldScience. 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Chapter7GlaciersResponsetoClimateChangeinSouthwesternChina7.1CharacteristicsofGlaciersChangeThereare23,221glaciersinSouthwesternChinawhichcoveranareaof229,523km,accountingfor50.16%oftotalareasand49.69%oftotalnumbersinChina(Shietal.2000).Throughthesortingofexistingresearchresultsonglacierchangeinthestudiedareainrecentyears,underthebackgroundofwarming,somephenomenahadbeenfound,suchassignificantglacialretreat,drasticalmasslosses,increasingglacialrunoffandtheexpandingareasoflakessuppliedbyicesorglaciers,reflectingtheobviousresponsetoclimatewarming.7.1.1TheGlacierRetreatandShrinkingAreasOnaverage,the102glaciersinGangrigabuMountainretreatedby1,095minthe2endof1915–1980,andthemeanareareducedby47.9km,eventheicereserves3decreasedby6.95km.52glaciersretreatedby237.2mintheendof1980–2001,2andtheareasreducedby12.42km.Meanwhile,theclimatechangewascharac-terizedbytemperatureriseandprecipitationincrease(Liuetal.2005a,b).Lanongglacier,zhadangglacier,panuglacierand50270C0049glacierinNyainqntanglhaMountainsretreatedbyrespectively381.8,489.5,377.2,and176.1mduring1970–2007.Xibuglacierretreatedby1,130.2m(Kangetal.2007)in1970–1999periodandGurenkekouglacierretreatedby293m(Puetal.2006)in1970–2003(Fig.7.1).TheglacierareaofRanwuhubasininsouthwesternTibetreducedby229.7kmfrom1980to2005,thereinto,theYanongglacierbasinwentback1,534m2anditsareashrankby2.33km.Inthesameperiod,thechangingtrendofannualmantemperaturewas1.34°CinBomistationsinthisregion,anditswarmingratewas1.36°C/10a.Thechangingtrendofannualmantemperaturewas1.34°CinChayustations,anditswarmingratewas0.20°C/10a.Thechangingtrendofannual©Springer-VerlagBerlinHeidelberg2015199Z.Li,StudyonClimateChangeinSouthwesternChina,SpringerTheses,DOI10.1007/978-3-662-44742-0_7 2007GlaciersResponsetoClimateChangeinSouthwesternChinaFig.7.1DistributionoftheobservedglaciersaandglacialbasinsbwithretreatingtrendinSouthwesternChinamantemperaturewas1.54°CinLinzhistations,anditswarmingratewas0.38°C/10a.Whiletherainfallofthreestationsbasicallykeptstable.Theglacierareaandice23reservesofPengqubasininXizangshrankby131.24kmand12.01km,respec-tively.Therewere99glaciershavingdisappeared.Thetemperaturewasonasig-nificantriseandthewidermarginofprecipitationchangeoccurredinadjacentDingristationin1961–2000wheretheprecipitationhadaslightincrease(Jinetal.2004).RuoguoglacierintheupstreamofYigongcangbuRiverretreatedby1,200mduring1959–1975(Shietal.2000).AzhaglacierinPalongzangbuRiverbasinretreatedby 7.1CharacteristicsofGlaciersChange2011,690min1980–2006,andPalongNo.4glacierretreatedby423mduring1980–2008.PalongNo.10,No.94andNo.390retreatedby30.5,41.2,and16.4m,respectivelyin2006–2008(Yangetal.2008a,b,c,2010a,b)(Fig.7.1).Since1970,thetemperaturerosesignificantlyinNamtsobasin,andthewarmingmagnitudeinwinterwasgreaterthaninsummer,butthesummerprecipitationincreasedsignifi-2cantly.Underthebackgroundofthis,theglacierareashrankby37.1kmin21970–2007.Thereinto,theareaofZhadangglacierreduced0.4km(Chenetal.2009).TheglacierinthesouthofRivergudiruinSilingCoretreatedby1,228min1969–2000(Luetal.2005).ThereducedglacierareainGeladandongregionwas214.91kmin1969–2000,atthesametime,thetemperaturerosesharply(Luetal.2002)(Fig.7.1).TheDongkemadiandlittleDongkemadiinMounttunggularetreatedby20.4and18min1994–1999(Puetal.2006).TheMapangyongcuobasinintheHimalayaregionexperiencedaglacier2reductionof7.53kmduring1974–2003(Yeetal.2008).Namunaniglacierhadaretreatof150mduring1976–2006(Yaoetal.2007a,b),anditsmeantemperatureinthesummerhalfyearandtheannualmeantemperatureroseby0.17and0.18°C.TheEastRongbuglacierandCentralRongbuglacierinEverestregionretreatedby198and315.5m,respectivelyin1966–2001,andtheFarEastRongbuglacierhadaretreatof230min1966–1997.Atthesametime,theclimateinthisregionpre-sentedadryclimatecharacteristic(Renetal.2003)(Fig.7.1).Theglacierareaof2protectionzoneinEverestshrankby501.91kmin1976–2006,thekeycauseofwhichwasthoughtamarkedincreaseinthetemperatureanddecreaseinrainfallbyanalyzing(Nieetal.2010).TheKangwureglacialofXixiabangmaPeakregionretreatedby303mfrom1974to2007,anditsareaandicereservesreducedby23respectively1.02kmand0.0481km(Maetal.2010).Dapusuoglacierretreated120mduring1968–1997(Puetal.2006).NamunaniPeakintheHimalayaregion2experiencedaglacierreductionof7.12kmduring1976–2003,mainlythecon-sequenceoftemperatureincreaseandprecipitationdecreasewasmeasuredatPulanstationneartheglacialregion(Yeetal.2007).Theglacierareaintheupstreamof2ManlareservoirintheHimalayaregionhadadecreaseof17.41kmin1980–2005.Whileoverthepast50years,theannualmeantemperatureroseby1.4°C,andtheprecipitationdidnotshowalong-termtrend(Lietal.2010a,c,d,e).From1970sto22000,theglacierareainBoqubasinandRuogebasinreducedby5.2and10.2km,respectively(Wu2004)(Fig.7.1).Comparedwith1966,theglacierareaofGonggaMountainreducedby6.36%in2002.SincetheobservationrecordsexistinginadjacentHailuogou,JiulongandXinduqiao,theanalysisontheannualprecipitationandannualmeantemperaturerevealedthattheannualmantemperaturehadbeenontheriseinthesethreestationsinlinewiththebackgroundofglobalwarming.ThetemperaturesintheeastslopeofGonggaMountainmeasuredbyHailuogoustationhadincreasedabout0.42°Cinthepast20years,andthetemperaturesinthewestslopeofGonggaMountainmeasuredbyJiulongandXinduqiaostationhadincreasedabout0.67°Cinthepast50years,whiletheannualprecipitationhadaslightchangeinbothslopes(Zhangetal.2010a,b).Hailuogouglacierretreated1,816.8mduring1930–2006,andtheHailuogouNo.2andYanzigouglaciersinGonggaMountainhadaretreatof1,075 2027GlaciersResponsetoClimateChangeinSouthwesternChinaand2,850m,respectively.WhiletheDagongbaglacierretreated450mfrom1930to2007.MingyongglacierinMeriSnowMountainhadretreatedby950min21932–2002.ThetotalglacierareainYulongSnowMountainreducedby3.11kmin1957–1999,andtherewerefourglacierhavingdisappeared.TheBaishuiNo.1glacierretreated830min1900–2008andtheannualmeantemperatureandpre-cipitationinnearbyLijiangstationdisplayedadecreasingtrendattherateof0.15°C/10aand14.2mm/10a,respectively(Lietal.2008a,b,2009a,2010a,b).Inaddition,thesurfacemorphologyofglaciershadchangedsignificantlyunderthebackgroundofacceleratingmelting.Forexample,theice-shelfcollapseofYang-gongRiverinYulongSnowMountainin2005(Zhangetal.2007a,b,c,d),thechangesoficetongueinAzhaglacier(Yangetal.2008a,b,c),theincreaseofthesubglacialwaterinHailuogouglacier(LiuandLiu2009)etc.allwerethetypicalfactsofseverechangesinglaciersurfacemorphology.However,notallglacierswereinaretreat.Therewerealsoapartoftheglacieradvancinginrecentyears.ThesummertemperatureofBomiandChayustationnearbyGangrigabuMountainincreasedby0.3–0.5°Cin1960–2002,duringwhichthemaximumtotalprecipitationinBomiandChayustationwere1.9and2.1times2oftheminimumprecipitation.Theglacierareainthisregionenlargedby10.4kmin1980–2001andadvancedby389m.Furthermore,the5O282B0136glacierand5O282B0123glacieradvancedrespectivelyby1,117and1,762m(Liuetal.2005a,b).Accordingly,Shietal.(2006)deducedthatiftheprecipitationinthehighaltitudeareahadincreasedassamemultiples,themainreasonoftheadvanceofglacierwereprecipitationincrease.Moreover,5K451F12glacierinGeladandongregionalsomovedforward680min1969–2000(Luetal.2002).7.1.2SevereMassLossofGlacierThemasslossofglacierwasanothersignificantfeatureofglacialchangesinthestudiedarea.AsshowninFig.7.2,Baishuihadaapparentmasslossin1952–2003,itsannualmeanmassbalancevaluewasthewaterequivalentof−218.8mminpast52years,andthethicknessoficetonguethinnedby15min2000–2004(Lietal.2009a,b).From1959/1960to2003/2004,thevalueofwatermassbalanceinHailuogouwas−10825.5mm(waterequivalent),andtheannualmeanvalueofmassbalancewas−240.6mm(waterequivalent).During1990/1991–1997/1998,theheightofmeltingicetonguewas6.84m,whichwasequivalenttowaterequivalentof6,157and876mmmorethanthatof1982/1983(Lietal.2008a,b,2009b,c,2010a,b).TheannualmeanthicknessofNo.4,No.10andNo.12glaciershadthinnedby5.2,4.5,and2.9m,respectivelyduring2006/2005–2007/2005(Yangetal.2008a,b,c)andtheannualmeanmassbalanceofNo.94,No.12andNo.10glaciersinthisbasinwerewaterequivalentof−748.7,−1,303and−517mmduring2005/2006–2007/2008,whiletheannualmeanmassbalanceofNo.4was−370mmduring2005/2006–2006/2007.TheannualmeanmassbalanceofDemulaglacier 7.1CharacteristicsofGlaciersChange203Fig.7.2DistributionoftheobservedglacierswithmasslossinSouthwesternChinawaswaterequivalentof−1,416mmduring2006/2007–2007/2008andthevalueofmassbalanceof24kglacierswaswaterequivalentof−1219mm(Yangetal.2010a,b).ThethicknessofZhadangglacierinNamucuobasinthinnedby11.2min1970–2007(Kangetal.2007),andtheannualmeanmassbalanceduring2005/2006–2007/2008waswaterequivalentof−591mm(Yaoetal.2007a,b).ThetheannualmeanmassbalanceofNamunaniglacierinthewesternHima-layaswas−685mmduring2004–2006.TheicereservesofNamunaniPeakhad3reduced3.06kmin1976–2001(Wangetal.2010a,b,c).7.1.3ExpansionofIceLakesorLakesSuppliedbyIcesAsshowninFig.7.3,theareasoficelakesinRanwuLakebasinofsouthwestern2Tibetincreasedby3.48kmfrom1980to2005(Xinetal.2009).Theareaof2NamucuoLakeexpanded72.6kmin1970–2007(Kangetal.2007).Zhuetal.thoughtthatthemainreasonsofexpansionofNamucuoLakewereregionalpre-cipitationincrease,severemeltinganddecreasedevaporationunderthebackgroundofclimatewarming,andthecontributionofmeltwaterreached50.6%.Theareaof2icelakeinSelincuoregionexpandedby221.72kmin1969–1999,(Luetal.2005)whichwascausedbytheincreaseofprecipitationandmeltwater.Theareasoficelakeshadexpandedby29%in2008thanin1970,andtheareasoficelakesindifferentheightshowedaexpandingtrend.Thepeakofnetincreasingareaappearedin5,000–5,300m,confirmingthesignificantwarmingofhighaltitudeareas. 2047GlaciersResponsetoClimateChangeinSouthwesternChinaFig.7.3DistributionoftheenlargedglaciallakesandbasinswiththeincreasedmeltingwaterinSouthwesternChinabasedontheobservationThefurtheranalysisholdaideathattemperaturesrise,glaciersretreat,increasingglaciermeltwaterwerethemaincausesoftheexpansionoficelakesinareas(Wangetal.2010a,b,c,2011a,b).TheareasofGaluncuoandKangxicuointheHimalayasregionincreasedby104and118%,respectivelyin2001thanin1987(Chenetal.2005).TheareaofLumuchimiincreasedby118%in2003thanin1977(Cheetal.2005a,b).Comparedwithin1975,theareasofwaterleveloffourlakes,suchasBamucuo,Pengcuo,2DongcuoandNairipingcuoexpandedby48.2,38.2,19.8and26.0kmin2005.Itsprimaryreasonswereanalyzedasthewarmandwetclimate,suchasrisingtem-peratures,increasingprecipitation,decreasingvaporizationandpermafrostdegra-dation(Bianetal.2006).ThelakeareaintheupstreamofManlareservoirhad22increasedto10.89kmin2005from8.33kmin1980,meanwhile,thetotalareaoflakesexpandedby30.8%(Lietal.2010a,c,d,e).Underthebackgroundofglobalclimatewarming,glaciersmelting,glaciersretreatandpermafrostdegradation,the2lakeareaalongS301highwayhadexpanded408.76kmin2000thanin1970(Wangetal.2008a,b).ThecomprehensivestudyofYaoetal.(2010)verifiedthatthesevereretreatofglacierswasoneofreasonsleadingtotheexpansionofregionallakeareas.StudiesconfirmedthatthecontributionrateoficeandsnowmeltwaterinHailuogoubasinis54.7%from1999to2004.Theanalysisfoundthattherunoff3willincrease2.6m/swhenthetemperaturesriseby0.1°Cinthisregion(Lietal.2008a,b).Comparedwithin1979–1988,therunoffincreased78.7%andthemeltwaterincreasedby90.9%,butprecipitationincreasedbyonly15.1%in1994–2003inYanggongRiverbasinofYulongSnowMountain(Lietal.2009a).Throughthecontrastofhydrologyobservationdatabetween1959and2005inRongbubasinofEverest,therewasawidermarginofincreaseintotalrunoffin 7.1CharacteristicsofGlaciersChange2052005thanin1959,andthemonthlymeanrunofffromJunetoAugustin2005increasedby69,35and14%thanin1959(Liuetal.2006a,b,c).Theanalysisonmultipleregressionofrunoffwithtemperatureandprecipitationsuggestedthatthetemperatureplayedaleadingroleinthechangeofrunoffinupstreamordown-streamofQugaqiebasininNamucuo,andtheleadingrolewasmorepronouncedinupstreamduetomoreproportionofglacierarea(Gaoetal.2009).Zhangetal.(2009)consideredthatthemaincharacteristicandconsequencesofchangesinclimateandglacierwerecommontemperaturerise,severeglacierretreatandtheexpandingicelakesintheHimalayasregion.Furthermore,theglaciersretreatwillleadtotheincreasedriskofglacierdisastersandhadalong-terminfluenceonriverrunoffandwaterresourcesinthisregion.7.1.4TheSignificantGlacierMeltSince1999,theobservationalstudiesofYulongSnowMountainwherethemon-itoredglacierswasBaishuiNo.1showedasignificantlyacceleratedglaciermeltwhichwasmainlyembodiedin:(1)Theglacierareaseverelyatrophied.Du(2011)foundthattheglaciersinYulongSnowMountainapparentlycontinuedtoshrinkin2recentyears.From1957to2001,thetotalareasofglaciershadreducedto5.30km2from11.6km,decreasingby54.31%,andtheannualmeandecreasewasabout220.138km.By2009,thetotalglacierareasreducedto4.42kmandshrankby261.90%thanin1957.Itsannualmeandecreasewasabout0.138km.Theanalysisconfirmedthatthecontractionrateofglacierareahadbeenaccelerating.(2)Theglaciermassshowedanegativebalance.Bycalculatingthedatameasured,Du(2011)foundthatthemassbalancevalueofBaishuiNo.1in2008/2009was−1,047mmandin2009/2010was−1,467mm.Comparedwiththesameperiodin1982,thedailymeanmeltin2009increasedfrom7.4to9.2cm,andthedailywaterlayerthicknessincreasedto75mmfrom37.(3)Theglacierfrontshadaobviousretreat.ThealtitudeofBaishuiNo.1glacierfrontsretreatedto4,365minJuly2010,whichroseby155mcomparedwiththesameperiodin1997.TheannualmeanretreatingspeedofBaishuiNo.1glacierfrontsin1998–2008was3.75mmorethanin1982–1998,andtheannualmeanretreatingdistanceoffrontsincreasedby7mcomparedwithin1982–1998.Moreover,thewidthatanaltitudeof4,680mofBaishuiNo.1glacierreducedby20min2004–2010.(4)Asig-nificantwarmingappearedinglacierarea.Theanalysisonthegradientmeteoro-logicalobservationdataandtheobservationresultsoficetemperatureindicatedthattheglacierareahadasignificantriseintemperature.Themeasuredresultsin2009showedthattheannualmeantemperaturesataltitudeof4,300mandnearbalanceline(elevationof4,800–5,000m)were2.1and1.5–2.5°Chigherthanin1982(Xin2011).In2008,theicetemperatureat5mdeepinanaltitudeof4,600mroseby0.41°Ccomparedwiththeobservationvaluesatthesameperiodin1982(Wangetal.2011a,b).Thesignificantwarmingintheglacierareawillleadtothesharpdecreaseincoldstorageofice,thenresultinthefasterglaciermelt. 2067GlaciersResponsetoClimateChangeinSouthwesternChina7.2ShorteningofGlaciersLength7.2.1CharacteristicsofStageinGlaciersLengthAsshowninFig.7.4,eightmarineglacierpresentastepchangemainlycharac-terizedbyretreatinrecent100years.Fromthebeginningofthe20thcenturyto1930s,inadditiontoBaishuiNo.1,theremaining7glacierswereinstableorforwardstate.Inthe1930s–1960s,theglacierswereinashrinkingstate.Hailuogouglacier,HailuogouNo.2glacier,Yanzigouglacier,BigGongbaglacier,LittleGongbaglacier,Mingyongglacier,AzhaglacierandBaishuiglacierretreatedby1,150,800,2,350,175,200morso,2,000,700and1,250m,respectively.From1960stoearly1980s,theglacierswereinastableorslowingdown.BigandLittleFig.7.4Variationofthelengthof8glaciersinsouthwesternChina.ReprintedfromtheLancet:Lietal.(2010c).Copyright(2010),withpermissionfromElsevier 7.2ShorteningofGlaciersLength207GongbaglaciersandHailuogouNo.2glacierwereinastablestate.YongmingglacierandBaishuiNo.1glaciermovedforward1,080and800m,respectively.Itwaseasytodeterminetheretreatingspeedofotherglacierssloweddownapparentlyfromthesmallertiltofbrokenlinethanformerstage.From1980stonow,alltheglacierswereinretreatingstate.Hailuogouglacierretreatedby491min1983–2006.HailuogouNo.2glacierandYanzigouglacierretreatedby300and200m,respectivelyin1981–1990.BigandLittleGongbaglaciershadaretreatof25mand12.5min1981–1990.BaishuiNo.1glacierwentback380min1982–2008,andtheMingyongglacierhadretreatedby30min1998–2002.7.2.2TheSpatialDifferenceofGlacierRetreatAsshowninFig.7.5,thereweredifferenceinchangingtrendsofeachglacierbecauseofthedifferencesinlatitudelocation,localclimatechange,localenvi-ronmentandglacieritselfcharacteristics(glacierlength,areaandgradient).Theyweremainlydisplayedinthefollowingaspects:(1)ThechangingtrendofglacierintheeastslopeofGonggaMountainwaswiderthaninthewestslopeinthesameperiod,andtheretreatingspeedinformerperiodwasremarkablyfasterthaninthelatterperiod.In1970s–1980s,theHailuogouandYanzigouglacierintheeastslopeofGonggaMountainshowedaslowretreat,whiletheBigandLittleGongbaglacierswereinastablestate.Themeltingoficetongueineastslopealsowasmorethaninthewestslope.Likewise,theGongbaglacierinthewestslopealsohadaslightretreatsince1980s.Theinvestigationin1982/1983confirmedthattheannualmeantemperatureandprecipitationofBigGongbaglacierfronts(3,700m)inthewestslopewere22°Cand1137.7mm,whereastheannualmeantemperatureandprecipitationofHailuogouglacierineastslopeatanaltitudeof3,000mwere3.9°Cand1,938mm.Furthermore,theprecipitationinglacieraccumulationarealocatedintheeastslopewasaround1,000mmgreaterthaninthewestslope(LiandSu1996).(2)AmongthreeglaciersintheeastslopeofGonggaMountain,becauseofthedifferencesinlocationandscaleofglacier,thechangingtrendofYanzigouglacierwithashorterlengthwasslightlygreaterthanthatofHailuogouglacier,whiletheretreatingspeedofHailuogouglacierwassignificantlygreaterthantheHailuogouNo.2glacierlocatedinsamebasinbuthadahigheraltitudeoffront.(3)Whentheinfluenceoftheglacieritselfcharacteristicswereignored,thereflectionofglacieratlowaltitudetoclimatefluctuationswasstrongerthanthatofglacierathighaltitude.During1930–1966,theMingyongglacierinlowerlatituderetreatmostfastly,andtheretreatingspeedofBaishuiNo.1glacierwhichwaslocatedatlowerlatitudebuthadahigheraltitudeoffrontwassimilartothatofHailuogouNo.2locatedinhigherlatitude.Inaddition,inthecoolingphaseof1970s–1980s,MingyongglacierandBaishuiNo.1glaciershowedasignificantadvance,whiletheglaciersathighaltitudedis-playedasloworstablestate. 2087GlaciersResponsetoClimateChangeinSouthwesternChina001900-19301930-19661966-19831983-20061900-19301930-19661966-19811981-1990-5-5HailuogouglacierHailuogouglacierNo.1-10-10-15-15-20-20-25-30-25velocityoffrontchange(m/a)Velocityoffrontchange(m/a)-35-30YearYear001900-19301930-19661966-19831983-199019000-19301930-19661966-19811981-2007-10-1Yanzigouglacier-2Dagongbaglacier-20-3-30ontchange(m/a)-4-40-5-50-6-60-7Velocityoffrontchange(m/a)Velocityoffr-70-8Yearyear00-0.51900-19301930-19661966-19811981-2007-51910-19301933-19731973-1980-1-10XiaogongbaglacierAzhaglacier-1.5-15-2-20-2.5ontchange(m/a)-25-3-30-3.5-35-4-40-4.5Velocityoffr-45Velocityoffrontchange(m/a)-5-5080year40Year6030BaishuiglacierNo.1Mingyongglacier402020010-201900-19301932-19591959-19711971-19981998-20020-401900-19571957-19821982-19971997-2008-10-60-20-80Velocityoffrontchange(m/a)Velocityoffrontchange(m/a)-100-30YearYearFig.7.5Variationvelocityof8glaciersduringthepast100years.ReprintedfromtheLancet:Lietal.(2010c).Copyright(2010),withpermissionfromElsevier7.2.3TheRelationshipofGlacierLengthandClimateChangeThetemperaturechangingtrendofChinawasbasicallyconsistentwiththenorthernhemisphereoverthepastcenturythatbothshowedafluctuationchangemainlycharacterizedbywarmingtrend.Theperiodfromtheendofthe19thcenturytothebeginningofthe20thcenturywasthecontinuouslowtemperaturestage,whiletheperiodfrom1930sto1960swasthecontinuoushightemperaturestage.Theperiodfrom1970stothemiddleof1980swasthelowtemperaturestage,andtheywereinaintenseheatingstatefrom1980stonow(Qinetal.2005).Thestudieshaveshownthatmarineglacierareaenteredintoashortcoldstage,thatisthebeginningof20thcentury.Thetemperaturerosebackfrom1930sto1960sbutdeclinedagainin1970s,whilebothtemperatureandprecipitationshowedasharpincreasingafter 7.2ShorteningofGlaciersLength2091980s(Heetal.2003a,b).Lietal.(2010b)confirmedthatthetemperatureofHengduanMountainpresentedthestatisticalsignificanceofwarmingtrend,andthewarmingmagnitudewas0.15°C/10a.Thereinto,thetemperaturewasrelativelylowin1960sand1980s,andthatinotherswerehigher.In2000–2008,theannualmeantemperaturewas0.46°Chigherthantheaverageformanyyears.TheannualprecipitationofHengduanMountainwaslowerin1960sand1970sandrelativelyhigherafter1980s,especiallythatin1990swas29.84mmmorethantheaverageformanyyears.Afterentering2,000,theprecipitationdeclinedapparentlycom-paredwiththatin1990s.Theannualprecipitationincreasedatarateofabout9.09mm/10ain1961–2008.TheanalysisofChaps.3and4alsoconfirmedthatthetemperaturecontinuedtowarmsince1961inSouthwesternChinaandacceleratedtoriseafterthemiddleof1980s.Whiletheprecipitationremainedstable.AsshowninTable7.1,bycontrastingthechangesof8glaciersfrontsinrecentyearswiththetemperaturechangesofChinaandNorthernHemisphere,icecorerecordsofDapusuo,recordsoftreeringsinHengduanMountainandtheclimatechangesofSouthwesternChinaandHengduanMountaininnearly50years,therewasobviouscorrespondencesbetweenthem.Thecoolingperiodfromtheendof19thcenturytothebeginningof20thcenturywhichwasthecoolanddryperiodofHengduanMountaininsummercorrespondedtothestabilityorrelativelyadvancingphase.Thewarmingperiodfrom1930sto1960swhichwasthewarmandwetperiodofHengduanMountaininsummercorrespondedtotheshrinkingphase.Thecoolingperiodfrom1970stothemiddleof1980swhichwasthecoolanddryperiodofHengduanMountaininsummercorrespondedtotherelativelystableorslowlyretreatstage.Thewarmingperiodfrom1980stonowwhichthewarmandwetperiodofHengduanMountaininsummercorrespondedtotheretreatstagesincethemiddleof1980s.Thesereflectedthattheglaciersadvancedorkeptstableincoldanddryclimateandretreatedorgotlossesinwarmandwetclimate.Itfullyshowedthatthetheinfluenceoftemperatureonmatteraccumulationandablationofglacierwasgreaterthantheinfluenceofprecipitation.However,thisdeductionstillremainedtobeseeninfurtherobservationalstudies.Heetal.(2003a,b)andPangetal.(2007)indicatedthattheglobalwarmingwasthemaincauseoftheglacierretreatinYulongSnowMountain.Aboveeachglaciershowedanobviousresponsetoclimatechange,fullyreflectedthehighsensitivityofchangesinglacierfrontstoclimatechanges,andtheaboveglaciersallwerethemarineglacierswithhighsensitivitytoclimatechanges.Strictlyspeaking,thechangesinfrontretreatdidnotfullyshowthesynchronywithclimatechange.Ontheonehand,itwasbecausethechangesinfrontretreathadaresponselagtoclimatechangeswhichformedbecausethedropoficethicknessandthesharpdecreaseofreservewerefirst,nextwastheretreatofwholefronts.Ontheotherhand,itwasbecausethedataofeightglacierchangeswasnotcontinuous,soitwasverydifficulttoreflecttheprocessofglacierretreatanditsspecificlag.Inaddition,theenvironmentofglacier(slope,altitudeetc.)andtheglacialfeatures(length,areaetc.)hadtheimportantinfluencesonthechangeofglacierfronts.Lijiangstationwithanaverageelevationof2,400mwaslocatedin25kmsouthofYulongSnowMountainwhichwassituatedatthenorthedgeofLijiangBasin.TheretreatspeedofBaishuiNo.1glacierin1998–2006increasedby7mthanin 2107GlaciersResponsetoClimateChangeinSouthwesternChina1970/1984/2003/–––178.8mmduring537.5mmduringchangeofHailuogouglaciermassbalanceis−1959/19601971Annualaveragemassbalanceis109.4mmduring1971/19721985massbalanceis−1985/19862004GlacierchangeMassbalanceSteadyoradvancingRetreatingAnnualaverageSteadyoradvancingorretreatingwithrelativelyslowervelocityRetreatingAnnualaveragemiddle1970s–Climatevariationrecordedby16cli-matestationsRelativetemperaturedecrease;precipitationdecreasedfrom1960sAcceleratingwarminganddecreasedprecip-itationafter1990sClimatevaria-tionecordedbyDasuopuicecoredecrease;steadyglacieraccumulationincrease;decreasedgla-cieraccumulationperaturedecrease;gla-cieraccumulationturerise;severeaccu-mulationdeclineuctuationandeightglacierschangeflClimatevariationincentralMt.HengduanandMt.YulongrrecordedbytreeringsColdanddryperiodRelativetem-WarmandwetperiodFasttempera-tioninChinaandtheNorth-ernHemisphereRelativelycoldperiodAccelerativeclimatewarmRelationshipbetweenclimate1920sColdperiod1960sColdanddryperiodWarmperiodTemperatureWarmandwetperiodmiddleTemperaturetoday––––Table7.1PeriodClimatevaria-1900193019701980sMiddle1980s 7.2ShorteningofGlaciersLength211Table7.2RelationshipbetweenchangeofBaishuiglacierNo.1andclimateinLijiangTemperature(°C)Precipitation(mm)Retreatvelocity(m/a)1982–199712.67947.389.41998–200613.311,062.7616.41982–1997.However,thetemperatureandprecipitationinlatterperiodwere0.64°Cand115.4mmgreaterinformerperiod.Moreover,thetemperatureofLijiangin1997–2004was0.54°Chigherthanin1982/1983,andthewaterequivalentofmeltingicetongueincreased113mm(Table7.2).Italsoindicatedthattheretreatperiodofmarineglacierwasinthewarmandwetweatherstage.Ontheonehand,thecoldstorageoficedroppedsharplyalongwiththerisingoftemperature.Ontheotherhand,theincreasingofnon-solidprecipitationfrequencyandtotalamountwouldfurtheracceleratethedisappearanceofglaciersbecausewhenthetemperaturechangesΔT≤0.5°C,theprecipitationchangescouldplayagreatroleontheglacierchanges;whenΔT>0.5°C,theglacierchangesweremainlydecidedbytemperatureratherthanprecipitationchanges(Gaoetal.2000).Since1998,thefrontschangesinaltitudeperformedasameoroppositetrendwiththechangesoftemperatureandprecipitation,andthedistanceoffrontsretreatalsoshowedasimilarchangewithprecipitationandtemperature(Fig.7.6),reflectingthatthesharpwarmingwasthemaincauseofsevereretreatofglacier.4320(a)14.520(b)RetreatdistanceTemperature14.54300FrontaltitudeTemperature10141442800C)C)426013.5o-1019981999200020012002200320042005200613.5o4240-2042201313-30erature(4200p12.54180-4012.5Temperature(Tem416012Frontvariation(m)-50414012Frontaltitudevariation(m)-60412011.5-7011.5199819992000200120022003200420052006YearYear4320(c)140020(d)1400FrontaltitudePrecipitationRetreatdistancePrecipitation4300101200120042800426010001000-101998199920002001200220032004200520064240800-2080042204200600-306004180400-40Frontaltitude(m)4160Precipitation(mm)Frontretreat(m)400Precipitation(mm)-502004140200-6041200-700199819992000200120022003200420052006YearYearFig.7.6RelationshipbetweenfrontaltitudeofBaishuiglacierNo.1andclimateinLijiangduring1998–2006(aandb);RelationshipbetweenfrontretreatofBaishuiglacierNo.1andclimateinLijiangduring1998–2006(candd).ReprintedfromtheLancet:Lietal.(2010c).Copyright(2010),withpermissionfromElsevier 2127GlaciersResponsetoClimateChangeinSouthwesternChina7.3NegativeBalanceofGlacierMass7.3.1BalanceofGlacierMassinHailuogouGlacierAsshowninFig.7.7,from1959/1960to2003/2004,themassbalancevalueofaccumulatedwaterofHailuogouglacierwas−1,0825.5mm(waterequivalent)andtheannualmeanbalancevaluewas−240.6mm(waterequivalent),indicatingthattheHailuogouglacierwasgivenprioritytolosefor45years,duringwhichtherewere16yearsshowingapositivebalanceand29yearsshowinganegativebalance.Twoturningpointexistedinmassbalancechanges:1970/1971and1984/1985.Onthebasisofthis,themassbalancewasdividedintothreestages:negativebalance(1959/1960–1970/1971),positivebalance(1971/1972–1984/1985)andseverelynegativebalance(1985/1986–2003/2004).Theanalysisfoundthatthewarmingperiodatthebeginningof1950s–1960swascorrespondingtothenegativebalancestage(warmandwetperiodofHengduanMountaininsummer)whenthethemassbalancevalueofaccumulatedwaterofHailuogouglacierwas−2,145.6mm(waterequivalent)andtheannualmeanbalancevaluewas−178.8mm(waterequivalent).Inaddition,therewerefivebalanceyearsduringthisperiod.Thecoolingperiodinthemiddleof1970s–1980swascorrespondingtothepositivebalancestage(coldanddryperiodofHengduanMountaininsummer)whenthethemassbalancevalueofaccumulatedwaterofHailuogouglacierwas1,532.2mm(waterequivalent)andtheannualmeanbalancevaluewas109.4mm(waterequivalent).Furthermore,Hailuogouglacierpresentedapositivebalanceandtherewereeightbalanceyearsduringthisperiod.Thestrongwarmingperiodinmiddle1980swascorrespondingFig.7.7VariationofmassbalanceinHailuogouglacierduring1959/1960–2003/2004 7.3NegativeBalanceofGlacierMass213totheseverelynegativebalancestage(warmandwetperiodofHengduanMountaininsummer)whenthethemassbalancevalueofaccumulatedwaterofHailuogouglacierwas−10,212mm(waterequivalent)andtheannualmeanbalancevaluewas−537.5mm(waterequivalent).Thisperiodwasthemostseverelynegativebalancestageandhadonlythreepositivebalanceyears(Fig.7.3).Inshort,themasslossedwasthemaincharacteristicofHailuogouglacierchangesfor45yearsbecausethemasslossescausedbythestrongwarmingalwayswasmorethantheslowincreaseofmassaccumulation.Inaddition,thetemperaturerisewouldleadtotheincreaseofthefrequencyandamountofliquidprecipitation.Andthen,ontheonehand,itcouldreducethematerialrechargeofice;ontheotherhand,thelatentheatreleasedbychangesinprecipitationformwouldacceleratethemeltingofglaciers.Fur-thermore,theappearanceofshortlypositivebalancemainlywastheresultoftemperaturedecreaseinthisperiod.7.3.2TheRelationshipBetweenMassBalanceChangesinHailuogouGlacierandClimateChangesAsshowninFig.7.8,themassbalanceinHailuogouglacierperformedaoppositechangetotheaccumulatedtemperatureofNorthernHemisphere,fullysuggested(a)(b)2000MassbanlanceTheNorhernHeimsphere8200012MassbanlanceChina7150015001061000100085C)oC)50045006o030419601966197219781984199019962002219601966197219781984199019962002arture(-500departure(-5002p1de-1000-10000Massbanlance(mm)0Massbalance(mm)-1500Cumulativetemperature-1500-2-1CumulativeTemperature-2000-2-2000-4YearYear(c)(d)200042000900MassbanlanceGanziMassbanlanceGanzi15001500800310001000700C)2o60050050050001019601966197219781984199019962002400-500196019661972197819841990199620020departure(-500300Massbalance(m)-1000-1000200-1CumulativetemperatureMassbanlance(mm)-1500-1500100PrecipitationinGanzi(mm)-2000-2-20000YearYearFig.7.8aTherelationshipbetweenmassbalanceandtheannualmeantemperatureoftheNorthernHeimsphere.bTherelationshipbetweenmassbalanceandtheannualmeantemperatureofChina.cTherelationshipbetweenmassbalanceandtheannualmeantemperatureofGanzi.dTherelationshipbetweenmassbalanceandtheannualmeanprecipitationofGanzistation.ReprintedfromtheLancet:Lietal.(2010d).Copyright(2010),withpermissionfromElsevier 2147GlaciersResponsetoClimateChangeinSouthwesternChinaoC)0.8(a)(b)Y=0.10785-1.52112E-4*X1.5R=-0.47;P<0.001Y=0.10785-1.52112E-4*X0.6FitlineR=-0.41;P<0.005C)oFitline1.00.4inChina(0.50.2NorthHemispherer(0.00.0departure-0.2-0.5TheannualaveragetemperatureTheannualaveragetemperature-0.4-2000-1500-1000-5000500100015002000departureinthe-2000-1500-1000-5000500100015002000Massbalance(mm)MassBalance(mm)Fig.7.9aThestatisticalsignificancebetweenmassbalanceandtheannualmeantemperatureofChina.bThestatisticalsignificancebetweenmassbalanceandtheannualmeantemperatureoftheNorthernHemisphere.ReprintedfromtheLancet:Lietal.(2010d).Copyright(2010),withpermissionfromElsevierthattheclimatewarmingwasthemainreasonofmasslossesofglaciers.Inaddition,theinterannualvariationofmassbalancealsoshowedasignificantlynegativecorrelationwiththoseofChinaandNorthernHemisphere,andthecor-relationcoefficientswere−0.47and−0.41,respectively(Fig.7.9).Itonceagainshowedthatthechangesinglaciersmassbalancewiththegeneraltrendofanegativebalanceresultedfromglobalwarming.Intheseverelynegativebalancestage,therisingoftemperaturecausetheacceleratedmeltingofglaciersandmadeglaciersinthestateoflosses.Whileinthepositivebalancestage,thedecreaseoftemperatureloweredthemeltingandshortenedthemeltingperiod.Conversely,theaccumulationincreasedandaccumulationperiodlengthened,thentheglacierswereinastateofincome.BycontrastingthemassbalancechangesofHailuogouwiththechangesintemperatureandprecipitationofGanziStationwhichwaslocatedinthenorthslopeofGonggaMountainand80kmawayfromHailuogou(Fig.7.8),itcouldbefoundthatthetemperaturealsopresentedanobviousriseandthechangesofmassbalanceandtemperatureshowedtheoppositetrends.Inaddition,theprecipitationshowedaslowincreasetrendandtherewasnoanobviousrelationshipbetweenmassbalanceandprecipitation,verifyingthatthetemperaturerisewasthemainreasonofglacierslossesandtheslightincreasedidnotfarrechargethemasslossescausebytemperaturesrise.Moreimportantistheprecipitationchangeinlowaltitudeisnotnecessarilysametothatinglacierareaathighaltitude.AsshowninTable7.3,innearlyhalfacentury,themassbalanceandclimatechangedisplayedanapparentcorrespondence.Themassgotseverelossesinwarmandwetperiod,whilethemasshadanobviousaccumulationincoldanddryperiodbuttheaccumulationwasalittleless.ThecorrespondingrelationwithtemperatureandmassbalanceinthechangingstagesandthesignificantlynegativecorrelationwithmassbalanceandtemperaturedemonstratedthatthemasslossesofHailuogouglaciermainlywastheresultofclimatewarming. 7.4IncreasingofGlacialRunoff215Table7.3RelationshipbetweenclimatefluctuationandmassbalanceClimatechangesofChinaandClimatechangesofHengd-ThemassbalanceNorthernHemispheresincetheuanMountainsince1900changesofHailuogouendof19thcentury(Shietal.(Fanetal.2008a,b,c)glacier2000)Warmperiodin1930s–1960sWarmperiodinThemeanmassbalance1930–1950s;Wetperiodinwas−178.8mmin1930–19601959/1960–1970/1971Relativelycoldperiodin1970s–-Coldperiodin1960–1985Themeanmassbalancemiddle1980sdryperiodin1960–1990was109.4mmin1971/1972–1984/1985ObviouslywarmperiodfromwarmandwetperiodfromThemeanmassbalance1980stotoday1990totodaywas109.4mmin1985/1986–2003/20047.4IncreasingofGlacialRunoff7.4.1ProcessofRunoffChangesinYanggongRiverAsshowninFig.7.10,in1979–2003,theprecipitationofLijiangandtherunoffofMujiaqiaowhichwasgeneralcontrolstationincreasedsignificantly,whichindi-catedthatunderthebackgroundofclimatewarming,therechargesanddischargesinLijiangBasinhadthesignificantincreases.Meanwhile,theincreasingtrendofminimumrunoffinMujiangqiaorevealedthattherechargeofgroundwatertosurfacerunoffinLijiangBasinremarkablyincreasedalongwiththeclimatewarming.InordertoanalyzetheresponseofrunoffinLijiangBasintotheclimatewarmingindifferentseasons,thisstudyconsideredtheperiodof1979–1988astheearlierstageofwarmingwhentheannualmeantemperaturewas12.8°Candtheperiodof1994–2003asthelaterstageofwarmingwhentheannualmeantem-peraturewas13.03°C,thencalculatedthepercentageofincreaseontheaverageofrunoffineverymonthintheearlierstageofwarmingtointhelaterstageofwarming(Fig.7.11).TheanalysisfoundthattherunoffofMujiaqiaoineverymonthsignificantlyincreased.Thereinto,itincreasedmostsignificantlyinspring(fromMarchtoMay),duringwhichthepercentageofincreaseinrunoffwasmorethan100%,whilethepercentagesofincreaseinrunoffinotherseasonswerelessthan100%(Fig.7.11).Therelatedstudieshaveshownthatunderthebackgroundofglobalwarming,themostsignificantwarmingappearedinwinterandspring(Bultot1988;MillerandBrock1989;DyurgerovandMeier2000).Therefore,thesignificanttemperatureriseinspringwillincreasethemeltwaterinthesnowandiceareasathighaltitudeinYanggongRiverbasinsothatthespringincreasingofrunoffwasthemaximuminMujiaqiaowherethespringmeantemperatureinformerperiodwas0.17higherthaninlatterperiod,(Fig.7.11).Intermsofchangeswithintheyear,therunoffwasmainlyrechargedbyunderwaterbecauseofthelessrainfallduringthedryperiod 2167GlaciersResponsetoClimateChangeinSouthwesternChina(a)(b)(c)Fig.7.10Annualtotalprecipitationvariationduring1979–2003inLijiang(a);annualaveragedischargevariationduring1979–2003inYanggongjiangbasin(b);annualminimumdischargevariationduring1979–2003inYanggongjiangbasin(c)(a)(b)Fig.7.11Theincreasedpercentofmonthlydischargebetween1994–2003and1979–1998(a);Theseasonalvariationofmonthlyaveragedischargebetween1994–2003and1979–1998(b).ReprintedfromtheLancet:Lietal.(2010c).Copyright(2010),withpermissionfromElsevier 7.4IncreasingofGlacialRunoff217(fromOctobertonextMay).Therunoffgraduallyreducedfromwintertospringandreachedtheminimuminlatespringbecausetherechargeofunderwaterwillgraduallyreduceasthetimegoing(Fig.7.11).FromtheFig.7.11,itcanbeseenthattherunoffdecreasedgraduallyfortheearlierstageorlaterstageofwarmingperiod.ButitgraduallyincreasedfromMayandreachedthepeakinSeptember,whichwastheembodimentofchangesinrechargeformaccordingtotheseasonsinYanggongRiverbasinbecauseitwasmonsoonperiodfromMay,andtheprecipitationwouldincreasesharply.Mostobviously,themonthlyminimumrunoffwasinMayintheearlierstageofwarmingperiod,whilethemonthlyminimumrunoffappeared1monthinadvance,thatisApril,whichsuggestedthatthewarminginwinterandspringmadetheiceandsnowmeltinYanggongRiverbasinhaveasignificantinfluenceonthetimeofrunoff,inaword,thepreactofmeltingperiodbroughtforwardtherechargingperiodoficeandsnowmeltandmadetherunoffinMayincrease(Fig.7.11).Underthebackgroundofglobalwarming,theinterannualandseasonalrunoffexhibitedanincreasingtrend,buttheincreaseinspring,summerandwinterallweremorethaninautumn,reflectingtheinfluenceofclimatewarminginaboveseasonsweremoreapparentthaninsummer.Ontheonehand,itsuggestedthattheseasonalpatternofregionalwarmingwasoneoftheimportantfactorsofchangesintheseasonalpatternofwatercycleinmarineglacierareasinthecontextofwarming.Ontheotherhand,thesummerandautumnrunoffwererechargedbyprecipitationinYanggongRiverbasinandtheprecipitationincreasewasnotveryobviousinthesameperiod,sotheincreaseofrunoffwasrelativelysmall.Inordertofurtherknowtheresponseofthechangesintheiceandsnowmeltwaterathighaltitudetoclimatechangesunderthebackgroundofwarming,wecalculatedtheinputofwaterPGlacieroficeandsnowregioninYanggongRiverbasin(altitude>4,000m)toLijiangBasineveryyearbyusingthewaterbalanceformulainChap.2,andfoundthatthePGlacierin1979–2003showedanobviousrisingtrend(Fig.7.12).Apparently,thecontributionoficeandsnowareaathighaltitudeinYanggongRiverbasintotherunoffofLijiangBasinincreasedyearbyyearwiththeclimatewarmingandtheseveremelting.Theaverageofcontributionformanyyearswaswaterequivalentof154.4mm.however,astheglaciersreservesdecreasedyearbyyear,theamountofcontributionwouldbegintofallbackwhenitreachedapeak,whichwoulddecreasethesecurityofregionalwaterresources.In1979–2003,averagePGlacieraccountedfor35.8%ofannualmeanrunoffinYanggongRiverbasinwhichmightbeahighervalue.Buriedriverchannelswerecomplexduetothecarbonatelandscapeinthisbasin,somorerunoffbecamethegroundwaterandprobablydischargedresearchedareabyundergroundriver,whichmadethesurfacerunofflesswithinthebasin.TheaverageofrunoffformanyyearsinMujiaqiaostationswas429mmwhichwassignificantlylessthantheprecipi-tationinsameperiod.Soifwewanttoaccuratelyunderstandthecontributionofwaterresourcesintheiceandsnowareaathighaltitude,itisverynecessarytostrengthentheresearchesongroundwatercirculationandtheconditionofwaterresourcesinrechargingbasininthefollow-upwork. 2187GlaciersResponsetoClimateChangeinSouthwesternChinaFig.7.12Annualoutputdischargevariationduring1979–2003insnow-glaciercoveredareaofYanggongjiangbasinTable7.4TheincreasedPrecipitationDischargePglacierpercentofprecipitation,(mm)(mm)(mm)dischargeandPglacierbetween1979–19889083001101994–2003and1979–19881994–20031,045536210%Increase15.178.790.9AsshowninTable7.4,theincreasingtrendofdischargeinYanggongRiverduringtheearlierstagewasgreaterthanduringthelatterstageofwarming.Thereasonswereasfollowing.Firstly,thegrowthofprecipitationinhighaltitudeareawasmorethaninlowaltitudeareaunderthebackgroundofglobalwarming(DyurgerovandMeier2000).Theobservationsconfirmedthattheannualmeantemperatureatanaltitudeof4,300and4,800–5,000m(balanceline)inBaishuiNo.1hadroseby2.1and1.5–2.5°Cthanin1982(Xin2011).TheannualmeantemperatureofLijiangmeteorologicalstation(2,400m)in2009was1.4°Chigherthanin1982.Secondly,theseveremeltinginYanggongRiverbasinduetowarmingledtothesignificantincreaseinmeltwater.Thetemperatureinlatterperiodincreasedby0.23°Cthanintheformerperiod,buttherunoffofMu-jiangqiaohadamoreremarkableincreasethantheprecipitationofLijiang.Themeanprecipitation(1,045mm)inlatterstageofwarmingperiod(1994–2003)increasedby15.1%thanthat(908mm)informerstageofwarmingperiod(1979–1988),andthemeanrunoffdepth(536mm)ofMujiaqiaoinlatterstageofwarmingperiodhadanincreaseof78.7%thanthat(300mm)informerstageofwarmingperiod.ChiewandMcMahon(1994)thoughtthattheprecipitationchangesalwayswereexpandedintheresponseonrunoffandthepercentageofrunoffchangewasabout2timesofprecipitationafteranalyzingtheimpactsofclimatechangeonthe28representativebasinsrunoffinAustralia.Obviously,thesignificantincreaseofrunoffinMujiaqiaocannotbeentirelyresultedinthe 7.4IncreasingofGlacialRunoff219precipitationincreaseinLijiang.Theresponseofglacierontemperaturefluctua-tionswasmoresensitivebecauseofthesmallerareaofglcaciersinYanggongRiverbasin,therefore,thedischargeofwaterinhighaltitudeareaduringthelatterstagehadrisenby90.9%thantheformerstage.Moreover,thesharpwarminginlatterstage(1994–2003)madethesnowlineheightsignificantlyriseandthemeltingareaexpandbuttheaccumulationareanarrow,whichcausedthatthesolidprecipitationatthehighaltitudeareasturnedintoliquidprecipitation(HiguchiandOhata1996).Itincreasedtheliquidprecipitationinglacierareasandthemeltwater.So,thetemperatureriseofYanggongRiverwasthemainreasoncausingthesignificantincreaseofrecharge(namelyPGlacier)inLijiangBasin.7.4.2ProcessofRunoffChangeinHailuogouAsshowninFig.7.13,therunoffofHailuogouin1999–2004increasedsignifi-3cantly,andtheannualmeanrunoffin2004increased3.33m/sthanin1999.Thetemperaturealsoshowedanobviousrise,whiletheprecipitationandvaporationhowedatrendofdeclinebutreductionoftheevaporationwasfarlessthantheincreaseofrunoff.Fromthecontrastbetween1999and2004,thevaporationreducedby103mmandtheprecipitationdecreasedby55mm,whiletherunoffdepthwithaincreasingtrendwas1,334mm.Itindicatedthatunderthebackground(a)(b)(c)(d)Fig.7.13Thevariationofdischarge(a),temperature(b),precipitation(c)andevaporation(d)during1999–2004inHailuogoubasin 2207GlaciersResponsetoClimateChangeinSouthwesternChinaofclimatewarming,theacceleratingmelting,expandingmeltingarea,lengtheningmeltingperiodandlargercoverareaofglacierswhichaccountedfor37.7%oftotalareasresultedinmoreandmorerechargeoficeandsnowmeltingwatertorivers.Becausethemarineglacierswerelocatedinmonsoonregionatlowlatitudeandhadastrongersensitivitytoclimate,theweakwarmingwouldleadtoanonlinearincreaseofmelting,whichacceleratedtheglacierlossesandthespeedofwatercycletoacertaindegree.Furthermore,rechargeofglacierstothebasins(Pglacier)in1999–2004showedatrendofobviousrise(Fig.7.14).Theaveragewaswaterequivalentof2,024.6mmformanyyears,demonstratingtheimportantcontributionofglacierstorunoffincrease.ThetemperatureofHailuogouin2003increasedby0.31°Cthanin1999,buttheprecipitationin2003was237.5mmlessthanin1999.Therunoffdepthin2003hadanincreaseof681.44mmcomparedwith1999,atthesametime,Pglacieralsowaswaterequivalentof790.81mmmorethanin1999,whichsuggestedthattheincreaseofdischargeinglacierarearesultedfromtem-peratureriseplayedanimportantroleontheincreaseofrunoffwithinthebasin(Tables7.4and7.5).Inaddition,theseasonalchangeofprecipitationandrunoffdepthinHailuogou(Fig.7.15)showedthatthepeaksofprecipitationandrunoffdepthoccurredinJuneandAugust.AndtheprecipitationsinOctoberandAprilwerequitesimilarbuttherunoffdepthinOctoberwas162mmmorethaninApril.Thebasinareaislesserandthereweremostbedrockmountainshere.Thehydrologicalstationwaslocatedin1kmawayfromtheHailuogouglacierfront.Theseconditionsdeterminedthattheconfluenceofprecipitationwithinthebasincouldnotbe2monthlaterthanthesurfacerunoffbecausetherechargeoficeandsnowmeltingwaterinthehighFig.7.14Annualoutputdischargevariationduring1999–2004insnow-glaciercoveredareaofHailuogoubasinTable7.5Meanannualprecipitation,runoffandPGlacierintheHailuogoubasinin1999and2003,allvaluesareinmmequivalentYearPrecipitation(mm)Runoffdepth(mm)MeanPglacier(mm)19992,1603,418.71,617.620031,932.54,100.12,408.41 7.4IncreasingofGlacialRunoff221350900PrecipitatipnRunoff800300700250600200500th(mm)p150400300100Precipitation(mm)200Runoffde5010000123456789101112MonthFig.7.15TheseasonalvariationbetweenprecipitationandrunoffinHailuogoubasinmountaintodownstreamsurfacerunoffhadalagtoacertaindegree.Itwasbecauseheconfluenceofmeltwateringlacierareaswasrelativelyslowduetoitselfwatercyclesystem.ThepreviousresearcheshadproventhattheHailuogouglacierhadacomplexundergroundwatercirculationsystemindicatingthatthechangeoftheglaciermeltingwaterdeterminesthechangeofwaterquantityinthewholebasintoalargeextent.Additionally,themeanPglacierofHailuogoubasinin1999–2004accountedfor54.7%oftheaveragerunoffdepthformanyyears,showedagainthattheiceandsnowmeltingwaterinHailuogouhadaprimaryroleontherechargeofRiver.7.4.3PossibaleEffectsofIncreasingDischargeatHighAltitudeHailuogoubasinandYanggongRiverbasinwererechargedbymarineglaciers,buttheirgeographicallocations,areas,altitudes,internalfeatures,etc.hadgreatdiffer-ences.Forexample,theglacierareainHailuogoubasinwassignificantlymorethanthatinYanggongRiverbasin.However,underthebackgroundofclimatewarming,theircontributionvaluesofglacierregiontowaterquantityareatasignificantincreasingstateintheinterannualscale,whichcanindicatethattheincreaseoficeandsnowmeltingwatercausedbyclimatewarminghadbeenshownindifferentmarineglacierregions.Therefore,tostrengthentheobservationofwatercycleinmarineglacierregioncannotunderstandthemechanismofwatercycleinthecontextofclimatewarming,butalsorevealtheinteractionofclimateandhydrologyinmarineglacierregionfromtheobservationalstudiesforalongtimeassotoprovideascientificbasisforglobalchangeandregionaldevelopment.Duetothehydrologyobservationforashorttimeandthelackofobservationdataontheelementsinsomeglacierareas,theequationofwaterbalancemadeinthisstudystillhadsomelimi-tations.Theresearchesonthemechanismofwatercycleandtheresponseonclimatewarminginmarineglacierbasinstillneedtomeasuredforalongertime. 2227GlaciersResponsetoClimateChangeinSouthwesternChinaIftemperaturescontinuetorise,iceandsnowmeltingwaterinmarineglacierbasinwillcontinuetoincreaseintheshortterm,andaseriesofdisasters,suchasfloods,landslidesandicerockcollapsewilloccuringreatquantities,combinedwiththeheavyrainandundertheconditionofsteepmountainssothatamajorinconveniencewillbebroughttoregionaltransportation,tourismanddevelopmentofproduction.Andtheglobalwarmingwillacceleratethehydrologiccycleinmarineglacierarea,aggravatewaterlossandsoilerosionandgenerateagreatthreatforsoilinmoun-tainousareaandecologicalenvironment.Since1980s,inordertodeveloptheregionaleconomy,theice-snowtourismresourcesgetthesufficientdevelopmentinmarineglacierareaandaseriesoffamoustouristareawerebuilt,suchasYulongSnowMountain,HailuogouinGonggaMountains,MerrySnowMountainetc.However,underthebackgroundofglobalwarming,thesafetyoflargetouristfacilitieslikeropewayneedtobefurtherargued.Andthesustainabledevelopmentandprotectionofice-snowtourismresourcesisparticularlyimportant,soitisverynecessarytoratio-nallyutilizeandprotecttheice-snowtourismresourcesandstrengthencomprehensivemonitoringandscientificresearchworkoftheglacierareasintypicalbasins.7.5FragmentationofGlacierMicrotopographyThechangeofglaciersurfacemorphologywastheembodyoftheaccumulationandlossofmass,energyconversionandmechanismchangescausedbyclimatechangeonglacialappearancecharacteristics.Itwasreferinparticulartothechangeofexternalcharacteristics,ofwhichessenceweretheglacialshrinkageandmasslossescausedbyclimatewarming.Andthechangeofexternalcharacteristicsweredisplayedbythicknessdecrease,wideningandincreasingice-cranny,icecollapses,runoffincrease,channelexpansion,theformationandbreakofglacialdriftsandsome.Theadaptivemechanismsofglaciersreferredtoitselffeedbacksystemofresistingexternalforceslikeerosionanddestructionbyitsownintegrity,coldstorage,materialfeedbackmechanism,energyexchange,rheologicalstructure,materialexchangeandsurroundingenvironmentfactors.Thesurfacemorphologychangemainlycharacterizedbymasslossesdestroyedtheintegrityoftheglacier,expandedtheareasacceptingexternalforce,increasedthestrengthanddepthofoutsideinfluenceandacceleratedthemelting.7.5.1SurfaceMorphologyChangeofBaishuiNo.1TherecentinvestigationfoundthatthesurfacemorphologychangeofBaishuiNo.1inYulongSnowMountainpresentedthreecharacteristicsduetoclimatewarming(Fig.7.16).(1)Theicesurfacewasbrokenseriouslyintheablationareaandtherewerealotofice-cranny.Theicesurfaceoccurredobviousdifferencesinmeltingbecauseoftheeffectsoficestructure,slope,debriscover,glaciersmovementand 7.5FragmentationofGlacierMicrotopography223Fig.7.16Changesofice-crannyinaccumulationareaofBaishuiglacierNo.1(a,b);Changesofice-grooveinaccumulationareaofBaishuiglacierNo.1(c,d);ice-lakeinBaishuiglacierNo.1(e);ice-riversgrowninaccumulationareaofBaishuiglacierNo.1(f);Crashinginablationarea(g,h,i)others.Plus,thesurfacerunoffpoureddownwardalongice-crannyandresultedindrasticalbrokenicewhichbroughtagreatdifficultytoglacierobservation.(2)Themeltingwassevereinaccumulationareaandthedeepice-crannyincreasedyearbyyear,whichshowedatrendofgradualbreaking.Thereappearedseveraldeepice-crannieswhichwere30mdeepand1–3mwideandprofileofabout20mdeepand10mwideintheaccumulationareaofBaishuiNo.1glacier.Theformationofice-crannyandprofilewastheapparentsignofchanginginternalstructureandseveremelting.Especially,thecrannyandprofilehadthetendencyofdeepeningandwideninginashortperiod(Fig.7.16).Inaddition,theexplorationin2008dis-coveredthatsomesmalllakesandriversappearedintheicesurfaceinaccumulationarea(Fig.7.16).(3)Theiceshelfcollapsedfrequently.Itcanbeoftenseenthatthecollapsingicesfelldownbecauseoftherapidmelting,movementandabruptslope.ThemostseriouscollapsehappenedinYanggongRiverNo.5ofYulongSnowMountainin2003and2005.Zhangetal.(2007a,b,c,d)analyzedandfoundthatthedrasticalmeltingandacceleratingmovementwerethemainreasonofcollapseunderthebackgroundofclimatewarming,andtheinducementswerethehotanddryyearappearedsuddenlyaswellasthefavorableterrain. 2247GlaciersResponsetoClimateChangeinSouthwesternChina7.5.2SurfaceMorphologyChangeofHailuogouGlacierFigure7.17referredtothevariationsofHailuogouglacierfrontin1994,2004,2006and2007.In1994,therewaswhiteicesurface,lessdebriscoverandthickerglacier.Butin2004,duetotheseveremelting,thethicknessofglacierbecamethinnerobviously,andthedebriscoverbecamethickerandappearedinthewholeicesurface.Upto2006and2007,justsomeaccumulateddebriscovercouldbedis-coveredintheglacierfrontandalittleglaciericewasbefoundintheendofmeltwater.Furthermore,thelandwheretheglaciereverexistedinwascoveredbyrichplants,sothedebriscoverwas.Becauseofthesevereglaciermelting,therewastheobviousrunoffintheicesurfacecoveredbylittledebris(Fig.7.17).Undertheeffectofscouringoficesurfacerunoff,theiceholeformedandconnectedtheglaciertonguetosubglacialriversothattheeffectivelinkwasformedbetweenicesurfacerunoffandsubglacierrunoff(Fig.7.17).In2006,aice-crannyof1mwideand30mdeephadhinderedtheinvestigationofaccumulationareainHailuogouNo.2.ThethicknessofHailuogouglacierfronthadreducedby12mfor12yearsfrom1993to2004.Aglaciercavehadappearedinthegreatglacierwaterfallsince1990s.Andabigice-crannyof300mlongand20widewasinthemiddleofglaciertongue.Becausetheseveremeltingresultinthedecreasingthicknessofglacierandthesubglacierrivercausedthecollapse,bigandsmallcavesandcrannycouldbediscoveredinthesurfaceofglaciertongue,whichresultedintheunevennessoficesurfacecoveredbydebris.Theseveremeltingcausedmanycranniesappearinginthearchareaofglaciersandeventuallymaketheglacialarchdisappear.ThecontinuousretreatandthinningledtothedisappearanceofthefamousholewhichwastheentranceofsubglacierriverintourismareaofHailuogou.Fig.7.17ThevariationsofHailuogouglacierfrontin1994(a),2004(b),2006(c)and2007(d);ice-riversinHailuogouglaciertongue(e);theentryofsubglacialriversofHailuogouglacier(f) 7.5FragmentationofGlacierMicrotopography2257.5.3TheChangesofGongbaGlacierTheGongbaglacierinthewestslopeofGonggaMountainwasexploredinJune2007.AsshowninFig.7.18,thesurfacemorphologychangehasthreecharac-teristics:(1)Theentireglaciertonguealmostwascoveredbydebrisandtheglacierfrontcoveredbydebrisappearedmanycrannieswiththesevermeltingofglaciers,sothecollapsesandcaveswerefoundhereandthere.(2)Therewasaice-lakeofabout150mwideinthecrossofbigandsmallGongbaglaciers.Thislakeformedbecausetheglaciermeltwaterwasblockedbytheaccumulationofdebris.Whenitswaterlevelreachedacertainheight,theoutburstwasmostpossibleundertheconditionofspecialweather.Duetotheseveremeltingandthickdebriscover,thereweremanysmallmorainelakesandice-lakesdistributedinthewholeglaciertongueandcalled“Haizi”bylocalresidents.(3)Theglacierwaterfallcollapsedfrequentlywhichwasthecomponentofmostmarineglaciers.Undertheback-groundofclimatewarming,therapidmeltingcausedtheacceleratingmovementinthebottomofglaciersandfinallyresultedinthecollapse,whichindicatedthatthereducingofrechargeresourceandtheincreasingofmaterialcirculation.Generally,theglaciertonguewasrechargedthroughthesnowslideintheaccumulationareaofFig.7.18Abigice-lakeinthefrontofDagongbaandXiaogongbaglacier(a);asmalllakeinDagongbaglaciertongue(b);ice-fallhappenedinXiaogongbaglacier(c);ice-fallinDagongbaglacier(d) 2267GlaciersResponsetoClimateChangeinSouthwesternChinamostmarineglacierssothattheglaciertonguekeptinlowaltitude.Butnowitwasrechargedbyglaciercollapseandsnowslide,whichwasanotherobvioussignalofreducingmassaccumulationandsevereablation.7.5.4TheResponseofGlacierSurfaceMorphologyChangestoClimateChangeThecontinuouswarmingledtothesharpdropofcoldstorage.Ontheonehand,itspeededupthemelting.Ontheotherhand,itmademeltingareaexpand,meltingperiodlengthenandablationrateacceleratealongwiththechangesofinternalmechanismandglaciersurfacemorphology.Thechangesofglaciersurfacemor-phologyalsowerestrongevidenceofglacierchangeinthecontextofglobalwarmingbecausetheglacierchangewassolidandcomprehensivewhichwasnotdisplayedbythedecreaseoflength,widthanddepth,butalsobytheexternalmorphologicalchangesresultingfromthechangesofphysicalmechanism.Inaddition,thelocationofglaciersurfacemorphologychangesmovedtowardupstreamofglacierastherisingofsnowline,whichmadesomesurfacecharac-teristicsgraduallymovetoglacieraccumulationarea.Themanycollapsesandtheice-cranniesinsomemarineglaciersweretheprimeexamples.Thesechangeswouldfurtherundermineglaciersadaptivesystemandacceleratemelting,becausetheoccurrenceofbigcranniesdidnotdestroytheintegrityoftheglacierbutincreasedtheareaanddepthoftheoutsideinfluences.Moreimportantly,itwouldleadtotheinfiltrationofmeltwaterintocranniesandfurtheracceleratetheretreatandfragmentationofglacierswhichwasveryobviousinYuongSnowMountain.Moreover,thecollapseofbigicewaterfallinmarineglacierareawasoneofsignalsofrapidmelting.Thebigicewaterfallwasanimportantlinkbetweenaccumulationareaandglaciertongueandwasanimportantchannelofmaterialsupplyofglaciertongue.Inrecentyears,theexposedrockscausedbythecollapseoficewaterfallreflectedthattheaccumulationofmarineglacierscouldnotbalancethemasslossesresultedinseveremeltingofglaciertongueatlowaltitudeunderthebackgroundofsharpmelting.Itwouldleadtothegradualdisappearanceofglaciertongueandmaketheglacierchange.Forexample,thevalleyglacierscouldbecomecirqueglaciersorhangingcirqueglaciers.Theice-shelfcollapsewasanotherperformanceofrapidablationofmarineglacier.Thedrasticalmeltingwouldresultintheacceleratingmovementinthebottomofglacierandthecollapseoccurredundertheconditionofsteepslopeandterrain.Whentheglaciertonguemovedtoacertainlocation,thepossiblecollapsewaspossibleforsomebigglaciers,whichdidnotcausetherapidretreatbutthenaturaldisasterslikefloodandlandslides. 7.6Summary2277.6SummaryBysortingandanalyzingglacierobservationdataandpreviousstudies,theresponseofglaciersinSouthwesternChinatoclimatechangearemainlydisplayedasfollowing:(1)Underthebackgroundoftemperaturerise,especiallythefurtherwarminginhighaltitudearea,theglacierchangesinSouthwesternChinashowedfourcharacteristics.Thefirstissharpretreatandshrinkingarea.32glaciersinNyainqntanglhaMountains,Himalayas,TanggulaMountainsandHengduanMountainshadobviousretreat,andtheareasof13glaciersshranksignifi-cantly.Thesecondismasslossesofglaciers.ThemassofNo.94glacier,No.12glacier,No.4glacierandNo.10glacierinNyainqntanglhaMountains,Demulaglacier,ZhadangglacierinTanggulaMountains,NamunaniglacierinHimalayas,HailuogouglacierandBaishuiNo.1inHengduanMountainsshowedanegativebalanceinrecentyears.Thethirdisthesignificantincreaseoflakeareaandicerunoffrechargedbyglaciers.TheiceareaofSelincuo,Naqu,Namucuo,HimalayasMountain,theupstreamofManlareservoirandRanwuhubasinhadaincreasingtrend.Therechargeofsnow-icemeltingwaterinHailuogoubasin,YangjiangRiverbasin,RongbuRiverbasinandQugaqiebasintorunoffincreasedyearbyyear.Thelastoneissignificantlyacceleratedablationoftypicalglaciersmonitored.Itsmaincharacterswereseverelyshrinkingarea,acceleratedretreatofglacierfront,drasticallossesoficestorageandthesignificantwarmingofglacierarea.Thestudiessuggestedthatthetemperatureriseisamajorcauseofregionalglacierretreat,andprecipitationdecreaseinsomeregionsalsohasplayedanimportantroleintheglacialretreat,suchastheHimalayas.(2)Thechangeinlengthisthemostdirectresponseofglaciertoclimatechange.Underthebackgroundofclimatechange,eightmarineglaciersfrontsinHengduanMountainschangedindifferentstagesandthechangespresentedageneraltrendofretreat.Theperiodfromthebeginningof20thcenturyto1930swasthestableorforwardstage.Theperiodof1930s–960swastheretreatstage.Theperiodfrom1970stothemidof1980swasthestableorforwardstage.Andsince1980s,theglaciersretreatedsignificantly,buttherewasacertaindifferenceinchangingmagnitudeofglaciersduetothedifferencesofitsowncharacter-istics(length,area,altitude,slopedirection,etc.),environment,latitudelocationandsome.ThestudiessuggestedthatthechangeinlengthofeightglaciersobviouslycorrespondstotheclimatechangesinChina,NorthernHemisphere,SouthwesternChinaandHengduanMountain,andpresentsaforwardtrendincoldanddryperiodandbackwardtrendinwarmandwetperiod.(3)Thematerialbalancereflectsthedirectinfluenceofclimatechangeonglaciersfromamountofmass.During1959/1960–2003/2004,theaccumulatedwater-materialbalancevalueofHailuogoufor45yearswas−1,0825.5mm(waterequivalent),andtheannualmeanbalancevaluewas−240.6mm(waterequivalent),indicatingthatitwasgivenprioritytowithlossesfor45years. 2287GlaciersResponsetoClimateChangeinSouthwesternChinaDuring45years,thereare16yearsshowingpositivebalanceand29yearsshowingnegativebalance.ThestagedchangeofmassbalanceinHailuogouwasoppositetothatofChina,NorthernHemisphereandHengduanMountain,demonstratingthattheclimatewarmingisthemaincauseofmasslosses.(4)Theglacierhydrologicalsystemisasensitiveindicatorofclimatechange.In1979–2003,theprecipitation,meanrunoffandminimumrunoffincreasedsig-nificantly.Underthebackgroundofwarming,therechargingwaterofsnowandiceareaathighaltitudetoLijiangBasinincreasedyearbyyear,verifyingthattheincreaseofice-snowmeltingwaterwasthemaincontributiontotheincreaseofrunoff.Andtheaverageformanyyearswaswaterequivalentof154.4mm.Thetemperaturesroseby0.23°Cin1994–2003comparedwith1979–1988.Theprecipitationincreasedby15.1%inthesameperiod,butthemeanrunoffdepthwas78.7%inlatterperiodmorethaninformerperiod.ThedischargingwaterinthesnowandiceareaathighaltitudeinYanggongRiverincreasedby90.9%.Themonthlyminimumrunoffin+MujiaqiaoappearedinMayintheearlierstageofwarmingperiod,whileitoccurred1monthinadvanceinthelatterstageofwarmingperiod.Itindicatedthatthewarminginspringandwintermadetheice-snowmeltinYanggongRiverbasinplayanimportantroleonthetimeofrunoff.TherunoffofHailuogouincreasedsignificantlyfrom1999to2004andthetemperatureroseremarkably.Buttheprecipitationandvaporationshowedadowntrendinthesameperiod.However,therechargingwaterofhighaltitudetobasinhadaapparentrise,andtheaverageformanyyearswas2,024.6mm.ThetemperatureofHailuogouin2003was0.31°Chigherthanin1999,buttheprecipitationwas237.5mmlessthanin1999,andtherunoffdepthin2003was681.44mmhigherthanin1999.Atthesametime,thedischargingwaterofsnowandiceareaathighaltitudewas790.81mmhigherthanin1999.ThepeaksofprecipitationandrunoffdepthinHailuogouoccurredinJuneandAugust.Thesefactsshowedthatunderthebackgroundofclimatewarming,theseveremeltingledtomoreandmorerechargeofmeltwatertorunoff.(5)Thechangesinglaciersurfacemorphologyarealsorespondtoclimatechange.Thecontinuousriseoftemperatureledtothesharpdropofcoldstorage,ontheonehand,itspeededupthemeltingofglaciers.Ontheotherhand,itmadethemeltingareaexpand,meltingperiodlengthenandablationrateacceleratealongwiththesignificantchangesofinternalmechanismandglaciersurfacemorphology.Theglacierchangeissolidandcomprehensive,whichwasdisplayednotonlybythedecreaseoflength,widthandthicknessandthemasslosses,butalsobytheexternalmorphologicalchangescausedbythechangesofphysicalmechanism.Inaddition,thelocationofglaciersurfacemorphologychangesmovedtowardupstreamofglacierastherisingofsnowline.Therecentobservationhadconfirmedthatthechangesinglaciersurfacemor-phologyweremainlydisplayedbythethinningthicknessofglaciers,moreandbiggerice-crannies,thecollapseofice-shelf,increasingicesurfacerunoff,thechangesindebriscover,theformationandbreakofice-lakesandothers.Thesechangeswillfurtheracceleratethemelting,retreatandfragmentationofglaciers. 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Chapter8TheMainConclusionandProspect8.1ConclusionsBasedontheobservationdataof110meteorologicalstationsandtheNCEP/NCARreanalysisdata,thisstudysystematicallyresearchedthespatialandtemporalvari-ationsofannualmeantemperatureandprecipitationinSouthwesternChinaanditsinfluencingfactorsandfurtheranalyzedtheinterannualvariation,spatialdistribu-tionofextremetemperatureandprecipitationaswellasthecorrelationwithatmosphericcirculation,altitude,urbanheatislandandsomebycombiningsomeresearchmaterialsandusingavarietyofanalysismethods.Thisstudyalsoexploredthecharacteristicsandreasonsofspatialandtemporalvariationsofsunshinehoursfromwindspeed,relativehumidity,urbanizationprocess,cloudwatercontent,localterrainandsoon,andrevealedtheinfluencesofthelarge-scaleatmosphericcir-culation,regionalclimatewarming,horizontalpressuregradientandplateaumonsoononthetemporalandspatialvariationofwindspeed.Onthebasisofthis,thisstudyanalyzedandsummarizedtheresponsecharacteristicsofglaciersinstudiedareatoclimatechangesandthecorrelationwithglacierlength,materialbalance,glacierrunoff,surfacemorphologychangeandtheclimatechange.Someconclusionscanbemadeasfollowing.(1)Theannualmeantemperatureandprecipitationrespectivelywere12.7°Cand965mmin1961–2008.Thetemporalandspatialdistributionoftheannualandseasonaltemperatureandprecipitationgraduallyreducedfromsouthwesttonortheast.Inrecent50years,theannualmeantemperatureshadasignificantrisingattherateof0.33°C/10a.Thetemperatureincreasedsharplybeforethemidof1980sbutshowedaslightriseafterthemidof1980s.Theseasonaltemperaturechangealsoreflectedthesignificantincreasingtrend.In1961–2008,theannualprecipitationinthestudiedareaexhibitedanon-sta-tisticallyfaintreduce,andtheinterannualchangeskeptstablein1961–1980,slowlyfalldownduringthewhole1980s,thenincreasedapparentlyin1990sandhadawavelikedecreaseinnewcentury.Theprecipitationperformedan©Springer-VerlagBerlinHeidelberg2015233Z.Li,StudyonClimateChangeinSouthwesternChina,SpringerTheses,DOI10.1007/978-3-662-44742-0_8 2348TheMainConclusionandProspectincreasingtrendinwinterandspring.ThestationwithasignificantwarmingandawidermarginofwarmingweredistributedinXizangPlateau,HengduanMountainandYunnanPlateau,whilethestationswithanon-significantwarmingorcoolingweremainlylocatedinGuizhouPlateauandSichuanBasin.Inaddition,themagnitudeofwarmingincreasedwiththeriseofalti-tude,verifyingthewidermarginofwarmingintheheightaltitudearea.Thechangingtrendoftemperaturedeclinedinturnfromflatstation,intermountainstation,valleystationandsummitstation.Theurbanstationwasgreaterthantheruralstationsinthechangingtrendoftemperatureandthepercentageofstationwithasignificantwarming,whichresultedfromthedifferencesinaltitudesoftwotypesofstations.ThestationhavinganincreasingtrendinannualmeanprecipitationwereprimarilysituatedinXizangPlateau,HengduanMountain,thecentralandnorthwesternYunnan–GuizhouPlateau.AndthestationswithasignificantdecreasewerelocatedaroundSichuanBasin.ThemaximummagnitudeofincreaseanddecreaseinprecipitationoccurredinValleyStationandsummitstation,respectively.Regionalwarmingiscloselyassociatedwithchangesinlarge-scaleatmosphericcirculation.TheextremelyhightemperatureinsummersinthestudiedareawascontrolledbytwoanomalousanticyclonismwhichcausedthatthestrengtheningnorthwestwindinnorthernandeasternQinghai-XizangPlateauweakenedthepowerofsummermonsoonmovingnorthward.AndthenortheastwindofHengduanMountain,Yunnan–GuizhouPlateauandSichuanBasinalsohinderedthenorthwardtransportofseawatervapor,whichmadethestudiedareacontrolledbyhotanddryairmass.ThedifferencesofatmosphericcirculationbetweenextremelyhighandlowtemperatureinwintersindicatedthatthecyclonecirculationfurtherstrengthenedanddevelopedintosouthwestwindinNorthernChinawhichinturnweakenedtheintensityofwintermonsoon,limitedthemovementsouthwardandisbeneficialtothetemperaturerisewiththehelpofseawarmandwetcurrent.Thehighermeanwatervaporfluxinwinterandsummerduring1961–2008explainedtheincreaseoftheprecipitationinthestudiedarea.Therewasasmalldifferencebetweenwatervaporfluxesinwetyearsanddryyears.Insummer,onlythewatervaporfluxesintheeastandwestofXizangPlateau,thesouthofHengduanMountainandYunnanPlateauinwetyearswereslightlygreaterthanindryyears.Thesecirculationcharacteristicspartlyexplainedthefaintchangeofprecipitation.Inaddition,somestudiesfoundthatthenetlongwaveradiationflux,seasurfacetemperatureofwesternPacificandsunshinedurationhadplayedanobviousroleintheacceleratingwarmingafterthemidof1980s.TheprecipitationisalsosignificantlyassociatedwiththesubtropicalhighpressureofwesternPacific.(2)InadditiontoID(0.09d/10a),meanTX10(0.13d/10a),TN10(0.37d/10a),TXn(0.13°C/10a),TNn(0.29°C/10a),FD(0.29d/10a),DTR(0.18°C/10a),TN90(0.36d/10a),TX90(0.22d/10a),TXx(0.11°C/10a),TNx(0.17°C/10a)andtheGSL(0.12d/10a)showedstatisticallysignificantwarmingtrend,andthewarmingtrendincreasedafterthemidof1980s.Afterconstricting,itwasfoundthatthewarmingtrendofcoldnessindexandnight 8.1Conclusions235indexweregreaterthanthatofwarmthindexanddaytimeindex.Thechangingtrendofextremetemperatureindexinstudiedareawassignificantlygreaterthanthatinotherregionsofworld.Likeannualmeantemperature,thestationswithasignificantwarminginextremetemperatureindexweremainlydis-tributedinhightaltitudearea,andthestationswithanon-statisticalwarmingordecreasingtrendwerelocatedinYunnan–GuizhouPlateauandSichuanBasin.Furthermore,thewarmingtrendofextremetemperatureindexincreasedwiththeriseofaltitude.Themaximumofwarmingtrendoccurredinflatstationfollowedbyintermountainstation,valleystationandsummitsta-tioninturn.Comparedwiththeindexofextremetemperature,thesignificancelevelofchangesofextremeprecipitationindexwaslower.Onlythechangingtrendsofmaximum1-dayprecipitation(RX1day),consecutivewetdays(CWD)andextremelywetdayprecipitation(R99)hadpassedthesignificancetestamong11indexes.Theincreasingrainydaysathighaltitudeandtheincreasingrainintensityatlowaltitudecanbeverifiednotonlybythespatialdistributionofextremeprecipitationindexbutalsobythatitschangingtrendincreasedwiththeriseofaltitude.In1961–2008,verywetdayprecipitationandextremelywetdayprecipitation(R95andR99)hadthecontributionrateof34.2%toannualprecipitation.Thehighestfrequencyofextremeprecipi-tationeventoccurredinSichuanBasinwherethecontributionratewas41%.Theprecipitationindexofsummitstationshowedadeclinetrendandthemostindexesofflatstationalsowereonthedecrease,buttheprecipitationindexofvalleystationandintermountainstationhadincreased.Large-scaleatmosphericcirculationisthemaincauseofthechangeoftheextremeweatherevents.From1961–1985to1986–2008,Asiansummermonsoonsystemshowedatrendofweakening.Duetothis,thesummerandautumninstudiedareaweremainlycontrolledbyhotanddryairmass,leadingtoawidermarginofwarming.Furthermore,theprevailingnorthlywindhinderedthenorth-wardmovementoftheseawarmcurrentandresultedinlowerfrequencyoftheprecipitation.Thechangesofthecirculationsysteminwinterandspringreflectedtheincreasingintensityofwestwind.Underthisbackground,thesouthwestwindformedwithinNorthwesternChinaanditsnorthregions,andtheeastwindorsoutheastwindformedinSouthernChina.Thiswindfiledpatternwillweakentheintensityofwintermonsooninreverse,andeventuallycausethedecreaseofextremecoldevents.Comparedwithin1961–1985,inadditiontotheeasternXizangplateauandnorthernHengduanMountainwherethewatervaporfluxhadaweakincreasein1986–2008,otherregionsbasicallywasastablestate.Andthemeridionalalsodisplayedaapparentdeclinefrom1961–1985to1986–2008,indicatingthattheweakeningofmonsooncirculationandwatervaportransportandpartlyexplainedtheextremeprecipitationindexwithanon-significantchanges.Thecontributionofurbanheatislandeffecttowarmingtrendofextremetemperatureindexcannotbeignored.Thechangingtrendandthepercentageofurbanstationwithasignificantwarmingweregreaterthanthatofruralstation.Thisstudyconfirmedpreliminarilythatthecontributionrateofurbanheatislandtothe 2368TheMainConclusionandProspectwarmingtrendofcoldnessindexes(TX10,TN10,TXn,TNnandFD)andwarmthindexes(TNx,TNn,TN90andTX90)inresearchedareawere16.0and7.9%,respectively.(3)Theannualmeansunshinehourwas1894hinSouthwesternChina.ThemaximumoccurredinXizangPlateau,HengduanMountainandYunnanPlateau,andthesunshinehoursinGuizhouPlateauandSichuanBasinwerefewer.Theannualandseasonalsunshinehoursinstudiedareadecreasedbefore1990butincreasedsignificantlyafterward.In1991–2008and1961–1990,thestationswithdecreasingsunshinehoursweremainlydistrib-utedinlowaltitudearea,especiallyinGuizhouPlateauandSichuanBasin,whilethemoststationshadaslightdecreaseorapparentincreaseinhighaltitudeareas.However,themajorityofstationinthelowaltitudeareaincreasedsharplyin1991–2008.Thedecreasingtrendwasmaximuminflatstationfollowedbyvalleystation,intermountainstationandsummitstationsuccessively.Theincreasingmagnitudeofannual,spring,autumn,winterandwintermonsoonsunshinehoursinurbanstationweregreaterthaninruralstationsduring1991–2008,ofwhichfundamentalreasonswasthattheurbanstationsweremainlysituatedinlowaltitudearealikeYunnan–GuizhouPla-teauandSichuanBasinwherethedecreasingmagnitudeofsunshinehourin1961–2008wasgreatestandtheincreasingmagnitudein1991–2008wasmoresignificant.Windspeedisthemaincauseofthechangeofthesunshinehourinthestudiedarea.Thechangesinwindspeedandsunshinehoursshowedthesignificantlypositivecorrelationduring1969–2008inthestudiedareainadditiontotheautumn,andboththemhadthesamechangetendency.In1969–2000,thedecreasingmagnitudeofsunshinehourswasapparentlygreaterthanin2001–2008.Duringthesetwoperiods,thechangetendencyofsunshinehourhadasimilarspatialdistributiontothechangesofwindspeed.In1969–2008,thedecreasetendencyofsunshinehoursofstationswherethewindspeedwaslessthan1.5m/swasapparentlygreaterthanthethatofstationswherethewindspeedwasmorethan1.5m/sinstudiedareaexceptforthespringandautumn.Furthermoretheper-centageofstationswithadecreasetendencyinannualandseasonalsunshinehourwassimilartothesunshinehours.Thehumiditywasanotherfactorinfluencingthechangeofsunshinehours.Thechangesofhumidityandsunshinehoursshowedtwooppositetendenciesduring1961–2008,andthechangesofannualandseasonalsunshinehourshadthesignificantlynegativecorrelation.Additionally,solarradi-ationfluxreceivedbygroundsurface,cloudcover,wateramountincloudandprecipitationhadremarkableinfluencesonsunshinehour,particularlythechangesofsunshinehourin1970and1990.(4)Theannualmeanwindspeedwas1.75m/sinthestudiedarea,andthestationwithastrongerwindspeedwerelocatedinXizangPlateau,HengduanMountain,thecentralofYunnan–GuizhouPlateau,whiletheannualmeanwindspeedinmoststationsoftheeastandwestofYunnan–GuizhouPlateau 8.1Conclusions237andSichuanBasinwasweaker.Themeanwindspeedreducedsignificantlyattherateof0.24m/s/ain1969–2008.Thedecreaserate(0.37m/s/a)ofwindspeedin1969–2000wassignificantlyhigherthanin1969–2008,whilethewindspeedincreasedattherateof0.55m/s/10ain2001–2008.Theseasonalwindspeedshowedasimilarchangetendencytoannualwindspeed.From1969to2008,thedecreasemagnitudeofwindspeeddeclinedfromsummitstation,intermountainstation,andflatstationtovalleystationsuccessively.Thereweremorestationsshowingadecreasingwindspeedin1969–2000thanin1969–2008.Thesestationswerelocatedinhighaltitudearea.Thedecreasemagnitudedeclinedfromwesttoeastinspatialdistribution.In2001–2008,thestationsperformingincreasetendencyweredistributedinHengduanMoun-tain,YunnanPlateauandSichuanBasin,andthestationsexhibitingdecreasetendencyweresituatedinXizangPlateauandGuizhouPlateau.Inaddition,therootcauseofdifferencesinchangesofwindspeedbetweenurbanstationandruralstationwasthatthesetwotypesofstationsweredistributedindifferentaltitudes.Theaverageelevationofallruralstationswas2,692m,andtheaverageoneofallurbanstationswas1,156m.Thestationswithasig-nificantchangewereinhighaltitudearea.Thechangesinatmosphericcirculationarethemaincauseofthechangeofthewindspeedinthestudiedarea.TheanalysisfoundthatinadditiontothewestofXizangPlateau,themeridionalwinddecreasedfrom1969–1985to1986–2000instudiedarea,andthezonalwinddecreasedmoresharplyinlatterperiodthaninformerperiod.Itdemonstratedthattheweakeningofwestwindandmonsooncirculationmaybethemainreasonofthedecreaseofwindspeedbefore2000.Comparedwith1991–2000,thezonalincreasedsignificantlyduring2001–2008inadditiontoYunnanPlateau,indicatingthatthestrengtheningofzonalwindmaybetheimportantcontributorstotheincreasesofwindspeed.In1969–2008,Qinghai-XizangPlateauindexincreasedobviously,andannualandseasonalwindspeedhadthesignificantlynegativecorrelationwiththeplateauindex,reflectingtheapparenteffectofthestrengtheningofplateaumonsoononthedecreaseofwindspeedinthestudiedarea.Theregionalwarmingwasanotherreasonofdecreaseofwindspeedinthestudiedarea.Thechangesinwindspeedwereoppositetothatoftemperatureandhadasignificantlynegativecorrelationwiththetemperature,especiallytheminimumtemperature.Furtheranalysisfoundthatunderthebackgroundofasymmetricwarming,theannualmeanpressuregradientoflow-centrallatitudeareaandcentral-highlatitudeareaperformedadeclinetrend,suggestingthattheweakeningofpressuregradientwasthekeyincentivesofthedecreaseofwindspeed.Inaddition,sunshinehours,altitudeandsoonalsohadsomeeffectonthewindspeedchanges.(5)Underthebackgroundoftemperaturerise,especiallythefurtherwarminginhighaltitudearea,theglacierchangesinSouthwesternChinashowedfourcharacteristics.Thefirstissharpretreatandshrinkingarea.32glaciersinNyainqntanglhaMountains,Himalayas,TanggulaMountainsandHengduanMountainshadobviousretreat,andtheareasof13glaciersshrank 2388TheMainConclusionandProspectsignificantly.Thesecondismasslossesofglaciers.ThemassofNo.94glacier,No.12glacier,No.4glacierandNo.10glacierinNyainqntanglhaMountains,Demulaglacier,ZhadangglacierinTanggulaMountains,Nam-unaniglacierinHimalayas,HailuogouglacierandBaishuiNo.1inHengduanMountainsshowedanegativebalanceinrecentyears.Thethirdisthesig-nificantincreaseoflakeareaandicerunoffrechargedbyglaciers.TheiceareaofSelincuo,Naqu,Namucuo,HimalayasMountain,theupstreamofManlareservoirandRanwuhubasinhadaincreasingtrend.Therechargeofsnow-icemeltingwaterinHailuogoubasin,YangjiangRiverbasin,RongbuRiverbasinandQugaqiebasintorunoffincreasedyearbyyear.Thelastoneissignifi-cantlyacceleratedablationoftypicalglaciersmonitored.Itsmaincharacterswereseverelyshrinkingarea,acceleratedretreatofglacierfront,drasticallossesoficestorageandthesignificantwarmingofglacierarea.Thestudiessuggestedthatthetemperatureriseisamajorcauseofregionalglacierretreat,andprecipitationdecreaseinsomeregionsalsohasplayedanimportantroleintheglacialretreat,suchastheHimalayas.Thechangesoffrontwerethemostapparentreflectionofglacieronclimatechanges.Eightmarineglaciersfrontsinthestudiedareachangedindifferentstagesandthechangespresentedageneraltrendofretreat.Theypresentaforwardtrendincoldanddryperiodandbackwardtrendinwarmandwetperiod.Thematerialbalancereflectsthedirectinfluenceofclimatechangeonglaciersfromamountofmass.During1959/60–2003/04,theaccumulatedwater–materialbalancevalueofHailuogoufor45yearswas–10825.5mm(waterequivalent),andtheannualmeanbalancevaluewas–240.6mm(waterequivalent),indicatingthatitwasgivenprioritytowithlossesfor45years.During45years,thereare16yearsshowingpositivebalanceand29yearsshowingnegativebalance.ThestagedchangeofmassbalanceinHailuogouwasoppositetothatofChina,NorthernHemisphereandHengduanMountain,demonstratingthattheclimatewarmingisthemaincauseofmasslosses.Theglacierhydrologicalsystemisasensitiveindicatorofclimatechange.Astheclimatebecamewarmerandwarmer,therechargingwaterofsnowandiceareaathighaltitudeofYanggongRiverbasinin1979–2003andHailuogoubasinin1999–2004increasedremarkably,verifyingthattheincreaseofice-snowmeltingwaterwasthemaincontributiontotheincreaseofrunoff.Andunderthebackgroundofwarming,theseasonalstructureofglacierhydrologicalsystemwaschangingsignificantly.Forexample,comparedwith1979–1988,theminimumrunoffinYanggongRiverbasinduring1994–2003occurredonemonthinadvanceandthepeakvalueofrunoffdepthinHailuogoubasinlaggedtwomonthsbehindthatofprecipitation.Thechangesinglaciersurfacemorphologyarealsorespondtoclimatechange.Therecentobservationhadconfirmedthatthechangesinglaciersurfacemorphologyweremainlydisplayedbythethinningthicknessofglaciers,moreandbiggerice-crannies,thecollapseofice-shelf,increasingicesurfacerunoff,thechangesindebriscover,theformationandbreakofice-lakesandothers.Thesechangeswillfurtheracceleratethemelting,retreatandfragmentationofglaciers. 8.2Prospect2398.2Prospect(1)Thecomprehensiveutilizationofallkindsofmaterialisbeneficialtounder-standoverallprocessandregularofclimatechanges.ThedistributionofmeteorologicalstationsinSouthwesternChinaisuneven,especiallyinthewestofXizangPlateauwheretherearefewobservationstationexistingformanyyears.Andthemeteorologicalobservationsysteminthehighaltitude(above5,000m)isstillweak,whichrestrictstothoroughlyunderstandthewholeprocessofthetemperatureandprecipitationchangesinthestudiedarea.Althoughtherecordsoficecoresandtreeringathighaltitudecanbecon-sideredastheimportantbasisofresearchonclimatechange,thegreatdiffi-cultyinobtainingrestrictthewidespreaduseofthemwithinthewholestudiedarea.Therefore,aseriesofmeasures,suchassystematicallyanalyzingtheapplicabilityofvariousreanalysisdataandmaterialinSouthwesternChina,understandingthedifferencebetweenvariousdatasources,sortingandcom-paringthedifferentdatasets,applyingtheobservationdata,reanalysisdata,satelliteremotesensingdataandclimatemodeloutputintotheresearchesonclimatechangecontributetotheintegratedcognitionofprocessandregularofclimatechanges.(2)Abreakthroughofthefollow-upworkistodeeplyanalyzethecausesofclimatechange.Thereasonsofclimatechangearecomplexaswellasvarious.Duetothelimitationsofdata,information,andpersonalability,thisstudyexploresthereasonsofclimatechangeinSouthwesternChinafromafewaspects.Althoughsomemeaningfulconclusionsaremade,therearealotofunansweredquestions.Forexample,whatisthesunshinehourandSSTofwesternPacificrelatedtotheacceleratingwarmingafterthemidof1980s?Whatistherelationshipbetweencloudcoverandthedecreaseofsunshinehour?Howdothechangesofatmosphericcirculationandsurfacecondition(vegetation,urbanarchitecture)influencethewindspeed?thesolutionoftheseproblemsneedstoaccumulatemoreobservationdataforalongertimeandinformationandtousemorereasonablemethods,especiallythemodelsimulation.(3)Itismeanfultoassesstheinfluenceofclimatechangesonregionaldevelop-ment.FromtheconclusionofEasterlingetal.(2000)aboutthechangesinglobalextremeclimate,itisrevealedthattheprobabilityofextremeclimateeventsaroundtheworldincreasesyearbyyearoverthepastfewdecades,resultinginmorelossesindifferentfactors.SouthwesternChinaisthetran-sitionzoneofthefirstandsecondladderandbecometheareaoffrequentoccurrenceofgeologicaldisasterlikemud-rockflowduetothehighaltitude,specialgeologyandhydrology.Underthebackgroundoftheincreasingextremeclimateevents,particularlytheextremeprecipitation,allkindsofgeologicaldisasterswillbemorelikelytooccur.Soitisofgreatsignificancetostrengthenthemonitoringandforecastofextremeclimateeventsforregionaldisasterpreventionandmitigationandreducinglossesresultedfrom 2408TheMainConclusionandProspectmeteorologicaldisasters.Inaddition,withthechangesofwindspeedanddirectionaswellassunshinehour,whichchallengesandopportunitiesthedevelopmentofwindenergyandsolarenergyresourceswillfacealsoneedtobeexploredinfuturework.(4)Itisofsignificancetosystematicallyassesstheeffectofurbanizationprocessontheclimatechange.Intermsoftheeffectsofurbanheatisland,thisstudyjustfocusesonthecontrastofwarmingbetweenurbanstationandruralstationonbasisofpopulation.Butitdoesnotstrictlydefinetheurbanheatislandfrompopulationindex.Althoughthisindexhasbeenwidelyusedinlotsofresearchesathomeandabroad,itisstillneedstocomprehensivelyanalyzethechangesandtheinfluenceofurbanizationprocessfromlanduse,thermalconditionofbuildingmaterial,urbanlandscapelampatnightandothers.Additionally,thealtitudefactorneedstobedeductedinevaluatingthecon-tributionofregionalurbanheatisland.Bycomparingtheanalysisofsunshinehoursbetweenurbanandruralstation,theretwopointsneedtobeemphasized:Firstly,ifwiththeincreaseofaerosolconcentration,urbanizationprocesshadahugeimpactonsunshinehour,thesunshinehoursinRebanstationwouldreducesharplyafter1990.However,thesunshinehoursinSouthwesternChinapresentedaslightincreaseorstablestatefrom1990sanddidnotfallwiththequickeningpaceofurbanization.Secondly,thegreattreatmentofatmosphericpollutioninrecentyearsisimportantfortheincreaseofthesunshinetime,therefore,fornotallregions,thedecreaseinsunshinehourattributestotheinfluencesofhumanactivities,suchasatmosphericaerosol.Analysisfoundthatthewindspeeddoesnotweakenduetotherapidurbanizationprocess,whichalsohasbeenperformedintheresearchinwindspeedofChina.Iftheurbanizationprocesshadsignificantinfluenceonwindspeed,thewindspeedwouldreducebyawidermarginafter1990becausetheurbanexpansioninChinabeganintheendof1980sandearlier1990s.However,thewindspeedshowedastableorincreasingtrendafterthisperiod(Xuetal.2006;Gaoetal.2010).Moreover,thisphenomenonalsooccurredinthesoutheastofQueenslandandthenortheastofNewSouthWales,AustraliawhereareofhighurbanizationMcVicaretal.(2008).Thisinconsistentphe-nomenonbetweenwindspeedinurbanstationandtheurbanizationprocessmayreflectanotherinfluenceofurbanizationdevelopmentonwindspeed.Forexample,whentheurbanizationprocesshasdevelopedtoacertaindegree,itwillstrengthentheurbanatmosphericcirculationandresultintheincreaseofwindspeed.Certainly,thesespeculationsstillneedtobeverifiedinobser-vationdataandmodelsimulationforalongertime.(5)Theresearchonresponsemechanismofglaciertoclimatechangeisshortofmoreobservationdata.Temperatureandprecipitationaretwokeyfactorsresultinginthechangeofglaciers.ItisgenerallybelievedthatprecipitationplaysagreatroleonglacierchangewhentemperaturechangeΔT≤0.5°C;whenΔT>0.5°C,glacierchangeismainlydecidedbytemperature,andtheprecipitationdoesnotplayaleadingrole(Gaoetal.2000).Therisingmag-nitudeintemperatureof11stationsatmorethan4,000mofaltitudewas0.036 8.2Prospect241°C/ain1961–2008,andthetemperatureroseby1.73°Cfor48years.Accordingtoabovelaw,theglacierretreatwasmainlyaffectedbythetem-peratureriseinrecentyears.ThemeteorologicalobservationofBaishuiNo.1glacierin2009alsofoundthatthemagnitudeofwarminginthehighaltitudeareawasgreaterthaninthelowaltitude.Inaddition,theoccurrenceofpeakofincreasednetareaofglacierlakeat5,000–5,300mofaltitudeinHimalayasMountainssuggeststhewidermarginofwarminginthehighaltitudearea(Wangetal.2011).Temperaturerisecausesnotonlythedecreaseincoldstoragebuttheincreaseinfrequencyandamountofsolidrainfall,andfurtheracceleratesthemelting.However,thetemperatureisnottheonlyclimatefactorsaffectingtheglacierchange.Butbecauseofthelessobservationdataonprecipitationathighaltitudeandthecomplexityofprecipitationsysteminthemountainousarea,therealargeamountofobservationdatastillneedtobeaccumulatedtoknowitseffects.Thelocalposition,glaciersize,thealtitudeofglacierfronts,localclimateandsoonalsoaretheinfluencingfactorsofglacierchanges.Forexample,thetemperatureandprecipitationofHailuogouglacierintheeastslopeofGonggaMountainwerehigherthanthoseofGongbaglacierinthewestslope.Soglaciersintheeastsloperetreatfasterthanthoseinwestslope.TheretreatspeedofglaciersinthenorthslopeofEverestinHimalayasmountainswas50–83m/ain1973–1994,whiletheglaciersinthesouthslopeadvancedbytherateof58–105m/a,becausethepre-citationofsouthslopeisgreaterthanthatofnorthslope.PalongzangbuNo.94glacierretreatedfasterthanNo.390glacierin2006–2008,andthealtitudeofNo.94glacierfrontswas160mhigherthanNo.390glacierfronts.TheareaofFarEastRongbuglacierwasalittlesmalleranditsretreatspeedwasfasterthanthatofEastRongbuglacier,becauselargertheareaofglacierwasorhigherthealtitudeoffrontswas,theslowertheresponseonclimatechanges.Inaddition,Xuetal.(2009)discoveredthattheblackcarbonaerosolonthesurfaceofsnowandicehassig-nificantcontributiontotheaccelerationofglaciermelt.Yasunarietal.(2010)foundthattheglaciermeltcausedbyincreasedblackcarbonaerosolconcentrationonthesurfaceofsnowandicewillincrease70–204mmofmeltwaterrunoffwhichwillaccountfor11.6–11.6%ofannualrunoffofatypicalglacierinQinghai-XizangPlateau.TheassessmentofQianetal.(2011)showedthattheincreasedblackcarbonaerosolinthewholeQinghai-XizangPlateauwillmakethegroundsurfacetemperaturesriseby1.0°Candresultinsharpmelting.Undoubtedly,theeffectofthisfactoronmeltingofglaciersishuge.ThestudiesofTakeuchietal.(2011)andFlanneretal.(2007)alsoconfirmedtheaboveconclusion.Scherleretal.(2011)confirmedthatabout65%ofmarineglaciersinthesouthslopeofHimalayahadaretreattrend,butthefrontsofglacierscoveredbythickdebriswereonastability,reflectingtheimportanteffectofdebriscoveronprotectingglaciers.Aboveanalysisshowsthattheinfluencingfactorsofglaciershavediversityandcomplexity,andtheeffectsofthemonglacierchangeinSouthwesternChinastillneedtobeexploredinthefollow-upwork. 2428TheMainConclusionandProspectCurrently,ontheonehand,thelimitedobservationdataespeciallyinglacierareaisnotallowedtoexploretherelationshipbetweenglaciersandclimatechangefromquantification.Ontheotherhand,thedynamicsofresponseofglacierstoclimatechangestillneedtobeconstantlyimprove,becauseitchangesbasedonthedifferenttype,sizeandlocation.ThiscanbeprovenbytwospecialfactsinmarineglacierschangeofChinainthecontextofsameclimate.ThetemperatureandprecipitationinHengduanMountainincreasedby0.74°Cand44.5mm,respectivelyfrom1960to2008,andtheglaciershadasevereretreatandmasslosses.Thereare36glaciersadvancinginGangrigabuMountainlocatedintheeastpartofNyainqntanglhaMountains,andthetemperatureandprecipitationofadjacentBomistationincreasedby0.29°Cand70.8mminthesameperiod.Basicallyspeaking,ifwewanttoknowtheresponsemechanismoftheglaciertoclimatechange,wehavetomakeadeepexplorationfromglacierdynamicsandenergybalance.AlthoughtheseworkshasmadegreatprogressinsomeglaciersofNorthwesternChina,suchasTianshanNo.1glacierandQilianMountainNo.71glacier,thereisnoobviousprogressuptonowduetotheshortageofobservationdataandthegreatdifficultyinobtainingdata.Duetothesharpmelting,therechargingwateroficeandsnowareatobasinincreasesyearbyyear,resultingintheapparentincreaseinsurfacerunoffofsameglaciersinSouthwesternChinaandtheaccelerationofwatercirculation.Thisisacomprehensiveresponseofthesystemof“precipitation–glacier–groundwater–sur-facerunoff”toglobalwarming.Buttheconcretemechanismofitsresponseremainstobevalidatedbymoreobservationdata.Weinparticularneedtodevelopandstrengthenhydrologicalmodelsresearchoficeandsnowrelyingonobservationdata.Moreimportantly,aseriesofchangesofglaciersystemcharacterizedbymasslosseswillimpactontheeconomydevelopment,watercycle,disasterprevention,waterresourcesandecologicalenvironmentofglacierareainfluencedinSouth-westernChina.Therefore,itisofgreatsignificancetostrengthenthemonitoringofrunoffchangeinglacierarea.Moreover,itisanewdirectiontointensivelystudyglaciersmorphologychangesfromphysicsunderthebackgroundofwarming.ReferencesEasterling,D.R.,etal.(2000).Climateextremes:Observations,modeling,andimpacts.Science,289,2068–2074.Flanner,M.G.,etal.(2007).Present-dayclimateforcingandresponsefromblackcarboninsnow.JournalofGeophysicsResearch,112,D11202.Gao,X.Q.,etal.(2000).Discussionontherelationshipbetweenglacialfluctuationandclimatechange.PlateauMeteorology,19(1),9–16.(inChinese).Gao,H.,etal.(2010).Changesinnear-surfacewindspeedinChina:1969–2005.InternationalJournalofClimatology.doi:10.1002/joc.2091.McVicar,T.R.,etal.(2008).WindspeedclimatologyandtrendsforAustralia,1975–2006:Capturingthestillingphenomenonandcomparisonwithnear-surfacereanalysisoutput.GeophysicalResearchLetters,35,L20403. 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