Long term variations of monthly terrestrial evapotranspiration over the Tibetan Plateau(1982-2018)

Abstract

Evapotranspiration (ETa) is an important water balance component for the “Asia water tower”, Tibetan Plateau (TP). However, accurately monitoring and understanding the spatial and temporal variability of ETa components (soil evaporation Es, canopy transpiration Ec, and intercepted water evaporation Ew) over the TP remains very difficult, due to the scarcity of observational data for this remote area. Here, the 37 years (1982-2018) monthly ETa components on the TP were produced using the MOD16-STM model (Yuan et al., 2021), which uses the recently available datasets of soil properties, meteorological conditions, and remote sensing. The estimated ETa correlates very well with measurements from 9 flux towers, with low root mean square errors (RMSE=13.48 mm mon-1) and mean bias (MB=2.85 mm mon-1), and the coefficient of determination (R2=0.83) and the index of agreement (IOA=0.92). The annual averaged ETa for the whole TP (specified with an elevation higher than 2500m) is about 1028.22±37.8 km3/year. The main contribution of ETa on the TP comes from the soil, with Es accounted for more than 84% of ETa. The ETa showed a significantly increasing trend over most parts of the central and eastern TP and a significantly decreasing trend in the northwestern TP. The increasing rate of ETa in TP over the past 37 years is around 0.96 mm yr-1. The accuracy of this dataset is at the top of its class with cross-comparison validation with different existing datasets and independent site data validation. The new ETa dataset is useful for studying the impact of land cover change on hydrology and for water resources management of the whole TP, which has wide application value.  The V1 version of the dataset, with the time period of 2000-2018, contains 1076 files, which are simulated datasets (0.01°, monthly scale) of ETa, Es, Ec and Ew, as well as seasonal analysis, trend analysis and auxiliary datasets. For the convenience of users to download and use, in the V2 version, the dataset is added with 0.05° dataste, and the time scale is expanded to 1982-2018, containing a total of 3909 files. Information on the content of the data files can be found in the relevant literature and supporting information files.