基于信息扩散理论和多重分形理论的区域干旱特征分析

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1、万方数据4扬州大学硕士学位论文socialfactors．Theprobabilitydensityfunction(PDF)ofDSIisestimatedbyusingthemethodofinformationdistribution．ThevulnerabilityoftherelationshipbetweenDSIandDDIisconstructedbyusingthemethodoftwodimensionalnormalinformationdiffusion．Thentheaverageri

2、skcanbeobtainedbycalculatingthesum(discretedistribution)orintegral(continuousdistribution)oftheproductofthePDFofDSIandthevulnerabilitycurve．Theresultsshowthat，theintroductionofinformationdistributionanddiffusionmethodtoanalyzetheproblemofvulnerabilityforthes

3、ituationofsmallsamplecouldgetthePDFofDSIsmoother．What’Smore，thevulnerabilityoftherelationshipbetweenDSIandDDIthroughtheDSItogettheDDIhasclearerphysicalmeaning．Therefortheresultscouldberealistic．Moresignificantly，similarresultsCanbegot、析thdifferentsimplelengt

4、hwhichmeansthemethodisinsensitivetothesimplelengthanditCanovercometheinstabilityofanalysisofthesmallsample．ThenonlinearcharacteristicsofrecurrenceofdroughtinSouthwestChinawasanalyzedcombinedthemultifractaldetrendedfluctuationanalysis(MFDFA)andtheStandardized

5、precipitationindex(SPI、calculatedwitllthemonthlyprecipitationdataof303stationsinsouthwestChinaduring1961—2012reportedbytheChinameteprplogicaladministration，basedonthesimilarcharacteristicsofthetheoryofmultifractal．TheresultshowsthatthedroughtindexinSouthwest

6、Chinabelongtomultifractalsetsandareprovidedwithcharacteroflong-termcorrelationandthepropertyisuncorrelated、Ⅳjtlltimescales；Apower-lawdecaycanbeshownbothintheprobabilitydensityfunctionandautocorrelationofretumintervalsofdroughtevents，whchCanindicatethefacttha

7、tthereturnintervalsofdroughteventsexistmemorabilityandthememorydeclinegradually；Onthebasisoffurther，adroughtriskindexbasedonthecharacterofmultifractalandlong—termcorrelationWasputforward．Theindexwementionednotonlyreflectstheprobabilitydistributionandcharacte

8、rofmemoryofthereturnintevalsofdroughteventsbutalsoCandepictthedroughtriskinthefuture．Inaword，thedroughtriskindexwegothascertaininstructionsignificanceonjudgingthedroughthappenornotinthefuture，wh