Estimations of Regional Surface Energy Fluxes Over Heterogeneous Oasis–Desert Surfaces in the Middle Reaches of the Heihe River During HiWATER-MUSOEXE

Abstract

The determination of the spatial heterogeneity of the regional evapotranspiration over a complex underlying surface in an oasis-desert region is crucial for water resource management in a river basin and aiding in irrigation decisions. The surface energy balance system (SEBS) model has been widely used to estimate surface energy fluxes. However, the parameterization of surface roughness length for momentum transfer (z _0m ) and heat transfer (z _0h ) did not perform well for a complex underlying surface. Moreover, it is difficult to estimate surface soil heat flux, i.e., G ₀ , accurately at the regional scale. In this letter, the parameterization schemes of z _0m , z _0h , and G ₀ were optimized. Measurements from 21 sets of eddy covariance systems were used to validate the model performance. The results show that the revised SEBS model root-mean-square errors (RMSEs) of the satellite-based sensible and latent heat fluxes (H and LE) decreased from 97.2 W · m ^-2 to 56.9 W · m ^-2 and from 102.9 W · m ^-2 to 74.8 W · m ^-2 , respectively, at the footprint scale. At the pixel scale, the RMSEs of the revised model estimates of the H and LE were 40.9 W · m ^-2 and 57.5 W · m ^-2 , respectively. The improved agreements between the estimates and the measurements indicate that the revised SEBS model is appropriate for estimating regional energy fluxes over heterogeneous oasis-desert surfaces. Furthermore, the spatial and temporal patterns of the LE in the middle reaches of the Heihe River were investigated.