On the discrepancy of spatial variability-based models for regional evapotranspiration estimation

Evapotranspiration (ET) controls the water and heat transfer between land surface and atmosphere at different temporal and spatial scales. Given the different structures of the spatial variability-based SEBAL and T_S-VI triangle models but essentially the same definitions of the dry and wet pixels, this study aims to investigate through an analytical deduction and model applications how the SEBAL model and the T_S-VI triangle method differ from each other in the regional evaporative fraction (EF) and ET estimation. Results show that the SEBAL model produces more satisfactory latent heat flux (LE) estimates than the T_s-VI triangle method when compared with ground-based large aperture scintillometer measurements at the Yucheng station. The SEBAL-derived EF and ET values for most pixels over the study area are larger than those derived by the T_S-VI triangle method when the same group of dry and wet pixels is applied.