2022年8月13-14日青藏高原东北侧甘肃榆中地区出现极端暴雨事件，日降水量达130. 6 mm，最大小时降水量36. 6 mm，突破了该地区历史极值，造成了严重的社会影响和经济损失。本文利用地面分钟级气象观测以及高空观测、兰州多普勒天气雷达及欧洲中期天气预报中心第5代全球大气再分析产品（ECMWF Reanalysis v5，ERA5）等资料，通过分析此次极端暴雨中两个强降水阶段的观测特征、环境条件、地形影响和不稳定机制等。结果表明：（1）暴雨由西风带短波槽带来的弱冷空气和副热带高压外围的暖湿空气在陇中地区交汇引起，700 hPa 切变线提供了动力抬升条件，地面冷锋提供了触发条件。（2）暴雨过程雷达反射率因子表现为持久的强回波并伴有“后向传播”特征，存在低空急流和明显的辐合，在第二阶段冷锋后部回波顶高和第一阶段相当，但是范围更大，且结构更为紧密，对流云发展更加旺盛。（3）此次暴雨水汽条件充沛，第一阶段低层强烈辐合、上升运动以及较高的对流有效位能，存在显著的对流不稳定，第二阶段的上升运动有所减弱，对流有效位能为 0，动力及对流不稳定条件弱。（4）冷锋斜压锋生触发不稳定能量的释放是第一阶段降水的主要触发机制。冷锋过境后，第二阶段降水由地形、锋生次级环流及不稳定等共同作用形成。由于夏季冷锋后强降水在青藏高原东北侧地区并不常见，在业务中容易形成该类暴雨的漏报。因此，需要加强对此类过程的监测和预警。

On August 13-14，2022，an extreme rainstorm event occurred in Yuzhong region of Gansu Province， northeast of the Qinghai-Xizang Plateau. Accumulated daily precipitation reached 130. 6 mm and the maximum hourly precipitation was 36. 6 mm，breaking the heaviest daily precipitation records of the region and causing serious social impact and economic losses. Based on the data of surface minute observation and high altitude observation，Lanzhou Doppler radar and ECMWF Reanalysis v5（ERA5），by analyzing the observation characteristics，environmental conditions，topographic effects and instability mechanism of the two heavy precipitation stages in this extreme rainstorm，the results show that：（1）The rainstorm was caused by the convergence of weak cold air brought by the shortwave trough in the westerlies and warm and humid air outside the subtropical high in the Longzhong area. The 700 hPa shear line provided the dynamic lifting conditions，and the surface cold front provided the triggering conditions.（2）The radar reflectance factor in the rainstorm process was characterized by persistent strong echoes accompanied by "backward propagation"，low-level jets and obvious convergence. In the second stage，the echo top height behind the cold front was similar to that in the first stage，but the scope was larger and the structure was more compact，and the convective cloud development was more vigorous. （3）The water vapor conditions of the rainstorm were abundant. In the first stage，there was significant convective instability due to strong convergence and upward movement at the lower level and high convective effective potential energy. In the second stage，the upward movement was weakened，the convective effective potential energy was 0，and the dynamic and convective instability conditions were weak.（4）The release of unstable energy triggered by cold front baroclinic frontogenesis was the main triggering mechanism of precipitation in the first stage. After the transit of the cold front，the precipitation in the second stage was formed by the combination of terrain，frontogenic secondary circulation and instability. Since the heavy precipitation after the summer cold front was not common in the northeast part of the Qinghai-Xizang Plateau，forecasters tended to ignore such kind of rainstorms. Therefore，we need to strengthen monitoring and early warning of such rainstorm events.