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Evapotranspiration is a key part of the water cycle between the atmosphere and the land surface, and it is an important parameter for studying the land–atmosphere system. Change and evolution have important implications. Therefore, the understanding and research of actual evapotranspiration (AET) can profoundly affect water use, ecological environment, temperature, and precipitation. In this paper, the single-layer monthly average reanalysis meteorological data of the Qinghai–Tibet Plateau from 1981 to 2020 was used to study and calculate the actual evapotranspiration in the Qinghai–Tibet Plateau, and the temporal and spatial variation characteristics, variation laws, and changes were analyzed by methods such as cumulative anomalies and the Mann–Kendall trend test. The results showed the following: (1) The evapotranspiration gradually decreased from southeast to northwest. The evapotranspiration in the southeastern region is strong, and the maximum value appears in the Hengduan Mountains. (2) The evapotranspiration was the largest in summer and gradually decreased from southeast to northwest; the evapotranspiration in spring and autumn was relatively uniform, with little overall difference, and the evapotranspiration was the lowest in winter. (3) There were mainly three spatial distribution modes of evapotranspiration in the Qinghai–Tibet Plateau, which were characterized by a significant and consistent change centered on the Tibet region, an east–west reverse type, and an east–west "negative-positive-negative" of the distributed three-pole space. The corresponding time coefficients characterized the interdecadal and interannual variation, and the decadal variation characteristics are more significant than the annual variation characteristics. (4) The actual evapotranspiration had step change; the step change years were 1989, 2002, 2011, and 2015, and there was an interval of about 5 years. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau vortex (TPV) is a mesoscale weather system active in the near-surface layer, which is one of the major systems for the generation of precipitation in the Tibetan Plateau (TP). However, no long-term observations of the TPVs are available due to the scarcity of observations in the TP. Thereby, long-term, high-accuracy reanalysis products are a reliable source for the analysis of characteristic TPV activities and possible mechanisms behind. In the present study, an objective analysis method is implemented to obtain a complete dataset of TPV based on several reanalysis products, including the ERA-Interim, ERA40, JRA55, NCEP CFSR, and NASA MERRA2. The TPVs are detected and tracked by the minima in geopotential height at 500 hPa. Results indicate that the TPVs derived from multiple reanalysis products have quite similar spatial patterns and temporal variability. The characteristic parameters of the TPVs derived from a given reanalysis data are related to the resolution of this reanalysis product. Higher-resolution reanalysis products can yield more low-pressure systems, which explains why the TPVs derived from high-resolution reanalysis datasets generally have longer lifetime, stronger and larger vortex scale than those from low-resolution reanalysis products, although the total number of TPVs are similar. The annual average number of TPVs generated in the TP is 63.5, and these TPVs largely originate in the mountainous area of the central western TP around (34° N, 78–95° E) and a belt zone (30° N, 80–84° E) in the southern TP, where the elevation is around 5500 m. The TPVs often dissipate in low valleys and the lee side of mountains. They mainly occur in the warm season during May–September, most active in the summer and least active in the winter. More TPVs form in the daytime than in the nighttime. Those TPVs that move out of the TP account for less than 10–14% of all TPVs, and they usually follow three moving paths: eastward (6.9–7.8%), northeastward (2.3–3.4%) and southward (2.3–3.5%). [ABSTRACT FROM AUTHOR]