Recently, extreme precipitation has occurred frequently in the Tarim Basin, which has a fragile ecological environment, arousing widespread concern. Using daily precipitation observations from 42 stations in the Tarim Basin during the spring of 1980–2021 and monthly circulation reanalysis data from the European Center for Medium-Range Weather Forecasts Reanalysis v5, as well as statistical analyses and physical diagnostic methods, this study investigated the abnormal modes and the evolution characteristics and differences in atmospheric circulation. The results show that the spring precipitation anomalies in the Tarim Basin can be divided into two independent precipitation modes: the first (EOF1) is a precipitation pattern that is uniform throughout the region and the second (EOF2) is an east–west inverse pattern. Thus, there are distinct differences in the atmospheric circulation characteristics responsible for abnormal spring precipitation modes in the basin. When the precipitation across the entire basin is consistently excessive, the 500 hPa geopotential height is affected by the negative phase of the North Atlantic Oscillation related circulation, and anomalous negative geopotential height at 500 hPa and anomalous cyclone at 700 hPa control the entire Tarim Basin, favoring anomalous upward motion, and western and southwestern water vapor transport. This leaves the Tarim Basin with a net water vapor budget and abnormally high atmospheric precipitable water. The opposite situation occurs when the precipitation across the entire basin is consistently lower than normal. When there is a west-to-east precipitation gradient, the western part of the Tarim Basin is affected by the anomalous cyclone while the eastern part is affected by the amomalous anticyclone, leading to the east-west discrepancy. The western region of the Tarim Basin is dominated by upward airflow, whereas the eastern region is dominated by downward airflow, providing dynamic conditions for the west-to-east precipitation gradient. Under the influence of anomalous water vapor transport from the southwest and water vapor convergence, water vapor conditions favorable for precipitation can occur. The net water vapor in the basin also exhibited an abnormal west-to-east transport pattern. Moreover, the atmospheric precipitable water demonstrated an inverse phase distribution under the EOF2 atmospheric precipitation mode in the Tarim Basin.

中文翻译：

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中亚塔里木盆地春季降水优势平态及环流特征


近期，生态环境脆弱的塔里木盆地极端降水频发，引发广泛关注。利用 1980—2021 年春季塔里木盆地 42 个站点的逐日降水观测和欧洲中期天气预报中心再分析第 v5 版的月度环流再分析数据，以及统计分析和物理诊断方法，研究了大气环流的异常模态和演变特征和差异。结果表明：塔里木盆地春季降水距平可分为两种独立的降水模式：第一种（EOF1）是全区均匀的降水模式，第二种（EOF2）是东西向的逆模式。因此，导致流域春季降水模式异常的大气环流特征存在明显差异。当整个流域的降水持续过大时，500 hPa 位势高度受北大西洋涛动相关环流负相位的影响，500 hPa 的异常负位势高度和 700 hPa 的异常气旋控制着整个塔里木盆地，有利于异常的上升运动以及西部和西南水汽输送。这使得塔里木盆地的净水蒸气收支和异常高的大气可降水量。当整个流域的降水量持续低于正常水平时，会出现相反的情况。 当存在西向东降水梯度时，塔里木盆地西部受异常气旋影响，东部受非正常反气旋影响，导致东西向差异。塔里木盆地西部地区以向上气流为主，东部地区以向下气流为主，为西向东降水梯度提供了动态条件。在来自西南的异常水汽输送和水汽会聚的影响下，可能会出现有利于降水的水汽条件。流域内的净水汽也表现出异常的西向东输送模式。此外，塔里木盆地大气可降水在 EOF2 大气降水模式下表现出反相分布。