SEBAL-Sensitivity - New Mexico State UniversitySEBAL灵敏度-新墨西哥州立大学.pptVIP

ASensitivityAnalysisonRemoteSensingETAlgorithm—

RemoteEvapotranspirationCalculation(RET)JunmingWang,Ted.Sammis,LukeSimmons,DavidMiller,andCraigMeierAgronomyandHorticultureDept.NewMexicoStateUniversity

ObjectiveFindthekeyvariablesandequationsintheETestimatethataremostsensitivetochangeininputorchangeinfunctionswithinthecalculations.

ProcedureBuildthemodelValidateitSensitivityanalysis

BuildtheModel

ASTERSatellitefromNASA15by15mvisibleandnear-infraredradiance.Bands1-330by30mshortwaveinfraredradiance.Bands4-990by90minfraredradiance.Bands10-14Reflectance(Bands1-9)andtemperaturedatacanberequestedassecondaryprocesseddataAvailability:potentially16daysuponrequest

Reflectance

(resolution15by15m)BuildtheModel

Temperature

(resolution90by90m)BuildtheModel

Buildthemodel

Theory?ETins=Rn-G-HRnGH?ETinsGraphfromAllen,et.al.,(2002)BuildtheModel

NDVI=f(reflectance)H=f(NDVI,temperature,reflectance,solarradiation,windspeed)G=f(NDVI,solarradiation,reflectance)EndStart?ETins=Rn-H-GOutputdailyETGeneralflowchartRn=f(Rs,reflectance)BuildtheModelSatelliteinputs:surfacetemperatureandreflectance.Localweatherinputs:solarradiation,humidityandwindspeed

RnRn=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,averagedto90m2resolution.Rnl=f(RH,Ts)=netlongwaveradiationBuildtheModel

EmpiricalfunctionG=Rn*C

NDVIfromASTERreflectancedataofbands3and2,BuildtheModel

SensibleHeatFlux(H)H=(r×cp×dT)/rahHrahdTrah=theaerodynamicresistancetoheattransport(s/m).z1z2dT=thenearsurfacetemperaturedifference(K).GraphfromAllen,et.al.,(2002)BuildtheModelrah=ln(z2/z1)/(u*×k)u*=frictionvelocity

Selectionof“AnchorPixels”fordTcalculation“wet”pixel:Ts