Based on daily precipitation data from 115 climate stations, seasonal and annual precipitation and their extremes over the Tibetan Plateau and its surroundings (TPS) in 1963–2015 are investigated. There exists a clear southeast-northwest gradient in precipitation and extreme daily precipitation but an opposite pattern for the consecutive dry days (CDDs). The wet southeast is trending dry while the dry center and northwest are trending wet in 1963–2015. Correspondingly, there is a drying tendency over the wet basins in the southeast and a wetting tendency over the dry and semi-dry basins in the center and northwest in summer, which will affect the water resources in the corresponding areas. The increase (decrease) in precipitation tends to correspond to the increase (decrease) in maximum daily precipitation but the decrease (increase) in CDDs. Extreme precipitation events with 20-year, 50-year, 100-year, and 200-year recurrence occurred frequently in the past decades especially in the 1980s. The greatest extreme precipitation events tend to occur after the late 1990s and in the southeastern TPS. The ERA5 reanalysis and climate system indices reveal that (1) decreased moisture transports to the southeast in summer due to the weakening of the summer monsoons and the East Asian westerly jet; (2) increased moisture transports to the center in winter due to the strengthening of the winter westerly jet and north Atlantic oscillation; and (3) decreased instability over the southeast thus suppressing precipitation and increased instability over the northwest thus promoting precipitation. All these are conducive to the drying trends in the southeast and the wetting trends in the center.

中文翻译：

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1963–2015年青藏高原及其周边地区的年度和季节性降水及其极端事件

根据115个气候站的日降水量数据，调查了1963–2015年青藏高原及其周边地区（TPS）的季节性和年度降水量及其极端值。降水和极端日降水存在明显的东南-西北梯度，但连续干旱日（CDD）的模式相反。1963–2015年，东南湿润趋势干燥，而中部和西北部干燥趋势。相应地，夏季东南部的湿润盆地有干燥趋势，而中部和西北部的干，半干枯盆地则有湿润趋势，这将影响相应地区的水资源。降水量的增加（减少）趋于与最大每日降水量的增加（减少）相对应，而CDDs的减少（增加）则相对应。过去20年，20年，50年，100年和200年复发的极端降水事件频繁发生，特别是在1980年代。最大的极端降水事件往往发生在1990年代后期和TPS东南部。ERA5的再分析和气候系统指标表明：（1）由于夏季风和东亚西风急流减弱，夏季向东南方向的水分输送减少；（2）由于冬季西风急流和北大西洋涛动的加强，冬季向中心输送的水汽增加了；（3）东南部不稳定减少，从而抑制了降水；西北部不稳定增加，从而促进了降水。所有这些都有利于东南地区的干燥趋势和中部地区的润湿趋势。