Inter-annual variability of evapotranspiration and its response towestly and monsoon circulation over the Tibetan Plateau

In this paper, on the basis of the evaluation of the applicability of four gridded evapotranspiration datasets (GLDAS, GLEAM, MERRA-2, CRET) on the Tibetan Plateau, the most accurate CRET (R-2 of 0.84 and RMSE of 15.67 mm) and contemporaneous meteorological data are used to analyze the variability of evapotranspiration on the Tibetan Plateau on an interannual scale and its responses to the large-scale westerly and monsoonal. The results show that the annual mean evapotranspiration on the Tibetan Plateau is 414.2 +/- 18.32 mm, with obvious interannual variability and trends, and significant differences among regions (westerlies, monsoons and transition zones). The interannual variation of evapotranspiration is closely related to the interannual variation of the strength of the westerly and monsoon circulation, and there are significant regional differences in the influence of the monsoon and westerly winds on evapotranspiration. The westerlies and monsoons influence evapotranspiration by regulating local climatic environmental factors: soil moisture, normalized vegetation index (NDVI) and wind speed are the three main local climatic environmental factors regulating evapotranspiration on the Tibetan Plateau. The correlation coefficients between WYI and NDVI are large in the central and southern parts of the plateau, which makes the influence of WYI on evapotranspiration greate in the middle transition zone and the southern monsoon zone. WI is also significantly and positively correlated with soil moisture and NDVI, but the correlation coefficient between WI and NDVI is large in the central and northern parts, and the effect of WI on evapotranspiration is large in the middle transition zone and the northern westerly zone. Meanwhile, WI is significantly correlated with wind speed in most of the plateau, and WI has a positive contribution to evapotranspiration variation through wind speed in the eastern part of the plateau, making the interannual variation of evapotranspiration in the eastern part of the monsoon zone also influenced by WI, which finally makes the effect of WI on evapotranspiration is large in most of the Tibet Plateau other than the western part of the monsoon region. The results of the study can deepen the understanding of water cycle changes and their mechanisms on the Tibetan Plateau, and provide a scientific basis for water resources and ecosystem management.