Estimation of hourly actual evapotranspiration over the Tibetan Plateau from multi-source data

Actual evapotranspiration (ET a ) is an important component of the global energy exchange process and hydrological cycle. ET a data with high accuracy are of great significance to the understanding of hydrological processes and the regulation of local climate. In this paper, an ET a product with hourly temporal resolution for the entire Tibetan Plateau (TP) was proposed by using Fengyun-4A geostationary satellite data and a random forest (RF) model. Validation between RF-based ET a and in situ observations from six eddy-covariance stations over the TP showed a root mean square error (RMSE) of 0.991 mm day −1. Compared with the ET a results from the surface energy balance system (SEBS), maximum entropy production (MEP) and the European Centre for Medium-Range Weather Forecasts Reanalysis Fifth Generation (ERA5) with RMSE values of 1.997 mm day −1, 2.182 mm day −1 and 1.555 mm day −1, respectively, the RF model showed the best performance. The annual RF-based ET a over the entire TP was approximately 365.60 mm. Thus, the total water amount evapotranspired from the TP surface was approximately 9811.01×10 8 t yr −1. Additionally, diurnal, monthly and seasonal ET a variations in different land cover types and climate zones over the TP and their contributions to the total ET a were clearly quantified.