Evapotranspiration Disaggregation Using an Integrated Indicating Factor Based on Slope Units

This study proposes an evapotranspiration (ET) disaggregation model based on slope units. Different slope units are first delineated based on digital elevation model data with high spatial resolution. Key factors influencing ET variability across topographies, such as radiation, vegetation, and moisture, are integrated using Sentinel-2 and DEM data to construct an indicating factor. A slope-scale ET disaggregation model is developed using ETWatch data (1 km resolution) and the integrated factor, yielding reliable 10 m resolution ET data that reflect slope-scale variations. The validation in Huairou and Baotianman shows coefficients of determination of 0.9 and 0.91, respectively, and root mean square errors of 0.45 mm and 0.47 mm. Compared to the original 1 km resolution ET data, the disaggregated results show improved accuracy, with R2 values increasing by 1% (Huairou) and 2% (Baotianman) and RMSE decreasing by 21% and 13%, respectively. This model offers a novel approach for estimating forest evapotranspiration in mountainous areas and significant potential for water resource management and sustainable land–water allocation.