中亚低涡背景下南疆西部山区一次极端暴雨成因分析

利用南疆西部气象站观测、FY-2G 、ERA5 再分析及全球资料同化系统（GDAS）分析等资料，分析2022年5月28－31日南疆西部山区一次极端暴雨成因，探讨了中亚低涡背景下山区和平原降雨差异的主要原因。结果表明：极端暴雨发生在南亚高压呈青藏高压型的大尺度环流背景下，中亚低涡配合低层多尺度系统及复杂地形的影响下产生；中低层偏东气流是此次山区暴雨的必要条件，但暴雨不同时段其维持机制有差异；中小尺度对流云系不断合并加强形成的南北向云带持续影响是造成山区暴雨的直接原因；多路充足的水汽输送与山区陡峭地形强迫抬升造成山区持续性降雨；低层不饱和水汽条件是此次“东西夹攻”形势下平原地区降雨量级偏小的主要原因。

Cause analysis of an extreme rainstorm process in the western mountainous areas in southern Xinjiang of China under the background of Central-Asia vortex

By using the intensified surface observation data, FY-2G data, ERA5 reanalysis data and the analysis data from the global data assimilation system, the causes of an extreme rainstorm process in the western mountainous areas in southern Xinjiang of China on May 28–31, 2022 are analyzed in detail. Furthermore, the main reasons for the rainfall differences between mountainous areas and plains under the background of the Central-Asia vortex are discussed. The results show that the extreme rainstorm occurred when the South Asia high was in the “Qinghai-Tibetan high pattern”. The joint effect of terrain, middle-Asia low vortex, low-level systems has caused this extreme rainfall event. The low-level easterlies are the necessary condition for the development of this rainstorm episode. But, the rainstorm maintaince mechanisms are different at different rainstorm stages. The merging and developing of meso-small scale convective clouds leads to a north-south oriented cloud belt, which is the direct cause of the rainstorm in the mountainous areas. The terrain lifting effect and the convergence of meso-small scale systems are important favorable conditions for the heavy rainfall. The sufficient water-vapor support and the terrain-induced upward motion are the main reasons for the persistent rainfall in the mountainous areas. The low-level is dry, which is an important reason for the small rainfall in the plain areas under the situation of "east trough and west trough".