Comparison of Three Operative Models for Estimating the Surface Water Deficit Using ASTER Reflective and Thermal Data

Abstract

Three operative models with minimum input data requirements for estimatingthe partition of available surface energy into sensible and latent heat flux using ASTERdata have been evaluated in a semiarid area in SE Spain. The non-evaporative fraction(NEF) is proposed as an indicator of the surface water deficit. The best results wereachieved with NEF estimated using the “Simplified relationship” for unstable conditions(NEFSeguin) and with the S-SEBI (Simplified Surface Energy Balance Index) modelcorrected for atmospheric conditions (NEFS-SEBIt,) which both produced equivalent results.However, results with a third model, NEFCarlson, that estimates the exchange coefficient forsensible heat transfer from NDVI, were unrealistic for sites with scarce vegetation cover.These results are very promising for an operative monitoring of the surface water deficit,as validation with field data shows reasonable errors, within those reported in the literature(RMSE were 0.18 and 0.11 for the NEF, and 29.12 Wm-2 and 25.97 Wm-2 for sensible heatflux, with the Seguin and S-SEBIt models, respectively).

Keywords

• ASTER
• evapotranspiration
• surface energy balance
• semiarid.