SEBAL-Sensitivity-NewMexicoStateUniversitySEBAL灵敏度-新墨西哥州立大学

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1、ASensitivityAnalysisonRemoteSensingETAlgorithm—RemoteEvapotranspirationCalculation(RET)JunmingWang,Ted.Sammis,LukeSimmons,DavidMiller,andCraigMeierAgronomyandHorticultureDept.NewMexicoStateUniversityObjectiveFindthekeyvariablesandequationsintheETestimatethat

2、aremostsensitivetochangeininputorchangeinfunctionswithinthecalculations.ProcedureBuildthemodelValidateitSensitivityanalysisBuildtheModelASTERSatellitefromNASA15by15mvisibleandnear-infraredradiance.Bands1-330by30mshortwaveinfraredradiance.Bands4-990by90minfra

3、redradiance.Bands10-14Reflectance(Bands1-9)andtemperaturedatacanberequestedassecondaryprocesseddataAvailability:potentially16daysuponrequestReflectance(resolution15by15m)BuildtheModelTemperature(resolution90by90m)BuildtheModelBuildthemodelTheoryETins=Rn-G

4、-HRnGHETinsGraphfromAllen,et.al.,(2002)BuildtheModelNDVI=f(reflectance)H=f(NDVI,temperature,reflectance,solarradiation,windspeed)G=f(NDVI,solarradiation,reflectance)EndStartETins=Rn-H-GOutputdailyETGeneralflowchartRn=f(Rs,reflectance)BuildtheModelSatellitei

5、nputs:surfacetemperatureandreflectance.Localweatherinputs:solarradiation,humidityandwindspeedRnRn=Rns-Rnl=netradiationRns=(1-)Rs=netsolarradiationissurfacealbedo,=0.4841+0.3353-0.3245+0.5516+0.3058-0.3769-0.0015iisthereflectanceforASTERdatabandI,av

6、eragedto90m2resolution.Rnl=f(RH,Ts)=netlongwaveradiationBuildtheModelEmpiricalfunctionG=Rn*CNDVIfromASTERreflectancedataofbands3and2,BuildtheModelSensibleHeatFlux(H)H=(r×cp×dT)/rahHrahdTrah=theaerodynamicresistancetoheattransport(s/m).z1z2dT=thenearsurfacetem

7、peraturedifference(K).GraphfromAllen,et.al.,(2002)BuildtheModelrah=ln(z2/z1)/(u*×k)u*=frictionvelocitySelectionof“AnchorPixels”fordTcalculation“wet”pixel:TsTair“dry”pixel:ET0Ts=303KTs=323KBuildtheModelAtthe“wet”pixel:dTwet=Ts-Tair=0Shouldbeanalfalfafield,n

8、otcutandnotstressedforwaterAtthe“dry”pixel:Hdry=Rn–G-ETdrywhereETdry=0dTdry=Hdry×rah/(×cp)Shouldbeabaresoilfieldwhereevaporationiszero.BuildtheModeldTregressionBuildtheModelSensibleHe