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

Actual evapotranspiration (ETa) is an important component of the global energy exchange process and hydro-logical cycle. ETa data with high accuracy are of great significance to the understanding of hydrological processes and the regulation of local climate. In this paper, an ETa 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 ETa 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 ETa 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 ETa over the entire TP was approximately 365.60 mm. Thus, the total water amount evapotranspired from the TP surface was approximately 9811.01x10(8) t yr(-1). Additionally, diurnal, monthly and seasonal ETa variations in different land cover types and climate zones over the TP and their contributions to the total ETa were clearly quantified.