Retrieval Of Evaporation And Transpiration By Using Remote Sensing Model For Huang-Huai-Hai Region In China

Evapotranspiration is a very important component in mass and energy exchangebetween hydrosphere, atmosphere and biosphere. Traditional hydrological method forland surface evapotranspiration calculation is limited to fixed time and spacescale.With the research improvement of regional evapotranspiration,remote sensing isadded into kinds of estimation model,making it possible for the evapotranspirationcalculation of large spatial scale combined with meteorological data,which means alot for hydrology and water resources management,climate change and agriculturedevelopment.Among remote sensing evapotranspiration model, feature space method,which isbased on the trapezoid or triangle shaped by the scatter plot of land surfacetemperature versus vegetation index, is the research hotspot in recent years.The key toretrieve evapotranspiration by using feature space model is the determination of theoutline of trapezoid or triangle.This paper modified the algorithm to determine acturalboundary of the trapezoid and made it more accurate for lower boundary.On thisbasis,an operational two-layer model developed by Zhang Renhua was introduced,inwhich pixel component algorithm (PCACA) and layered energy algorithm is the corealgorithms,the former one was used to determine theoretical boundary of the trapezoidand the latter one was used to separate the available energy into vegetation latent heatand soil surface latent heat.In this research,Huang-Huai-Hai region was taken as study area.Remote sensingdata of MODerate-resolution Imaging Spectroadiometer, including land surfacetemperature,vegetation index,albedo products were used as well as meteorologicaldata of179stations in and around Huang-Huai-Hai region，such as wind speed,airtemperature,vapour pressure and so on.Then evaporation and transpiration wereretrieved by using the two-layer model, and the latent heat flux data observed by eddycovariance of Yucheng Station provided from China Flux net was used to calibrate themodel’s estimation result,the correlation coefficient(R2) reached0.87and the rootmean square error(RMSE) was below22.8w/m2.At last, spatial and temporaldistribution of evapotranspiration in Huang-Huai-Hai region was studied and therelationship between evapotranspiration and fractional vegetation coverage,leaf areaindex(LAI) and land cover type was analyzed,which consistently reflected the growthprocess of different type of crop.The proportion of transpiration in totalevapotranspiration was quantified over Huang-Huai-Hai region.