ALBEDO ACCURACY IMPACT ON EVAPOTRANSPIRATION ESTIMATION

摘要

In this work, we analyze the influence of estimating thernland surface albedo directly from the surface reflectancernor through the BRDF integration in the estimation ofrnenergy balance components such as the net radiation,rnlatent and heat flux and consequently in the land surfacernevapotranspiration. To this end, we processed remoternsensing and in-situ meteorological data measured at thernagricultural test site of Barrax in the framework of EarthrnObservation: optical Data calibration and InformationrneXtraction (EODIX) project. Remote sensing imagesrnwere acquisitioned for different View Zenith Anglesrn(VZA) by the Airborne Hyperspectral Images (AHS).rnResults have shown that albedo estimations derivedrnfrom BRDF model present stability through everyrnimage while albedo estimations using single reflectancernpresented high variation depending on the VZA. Thernhighest difference was observed in the backwardrnscattering direction along the hot spot region obtaining arnRMSE of 0.11 through the AHS image which implied arnrelative error of 65%. This work has analyzed the errorrncommitted by many evapotranspiration studies thatrnassume the surface as Lambertian and estimate thernalbedo from a surface reflectance weighted average.