A framework for validating remotely sensed evapotranspiration

Remotely sensed evapotranspiration (RS_ET) products have been applied from regional to global. However, the validation of remote sensing products over heterogeneous land surfaces has been hindered due to the challenges in the theory and methods in recent decades, especially in estimation of “ground-truth” at the satellite pixel scale. In this study, an innovative validation framework including quantification of the spatial heterogeneity, optimization of the ground sampling strategy, multi-scale measurement, upscaling theory, uncertainty analyses, and validation method (direct validation, indirect validation and cross validation), was proposed to validate RS_ET products at different scales. Here, the framework was applied in Haihe and Heihe basin in China. The results showed the proposed validation framework of RS_ET product was reasonable and feasible.