Intercomparison of remote sensing-based models for estimation of evapotranspiration and accuracy assessment based on SWAT

An intercomparison of daily actual evapotranspiration (ET) estimates from the single-source models (SEBAL and SEBS) and the two-source models (P-TSEB and S-TSEB) using remotely sensed data was performed to examine their utilities and limitations under a wide range of land covers and different meteorological conditions. The accuracy of ET estimates from remote sensing-based models of a selected watershed oil 23 June 2005 (DOY 174) presenting large air drying power and marked contrast in underlying surface characteristics, and 25 July 2005, (DOY 206) in contrast to the meteorological and underlying surface conditions of DOY 174, were evaluated in terms of SWAT-based ET. The ET estimates from the two methodologies are shown to be comparable, indicating that S-TSEB has the highest accuracy with relative errors of 2.2% and 5.6% with reference to SWAT-based ET for DOY 174 and 206, respectively. Hence it was selected to be the basis for performing an intercomparison with other remote sensing-based models. Single-source models are very sensitive to KB-1 parameter, rendering marked differences in ET estimate, because of different treatments of roughness length for heat transfer. SEBAL and SEBS yielded mean absolute percentage difference (MAPD) versus S-TSEB within 26.22% and 26.56% for DOY 174 and within 9.11% and 11.69% for DOY 206, respectively, indicating their applicability to higher vegetation cover and soil moisture availability areas under small air drying power condition. P-TSEB generated MAPD versus S-TSEB within 41.15% for DOY 174 and 8.79% for DOY 206. implying that P-TSEB is highly consistent with S-TSEB under small air drying power and less contrast in soil moisture conditions. whereas noticeable discrepancies occur under large air drying power and marked contrast in soil moisture circumstances, in particular for sparse cover. The performance of P-TSEB largely depends on the meteorological and underlying surface conditions, both exerting significant influences oil the extent Of Coupling between vegetation and soil. Copyright (C) 2008 John Wiley & Sons, Ltd.