基于多源观测资料的芜湖“7·19”短时暴雨过程分析

Analysis of the “7·19” Short-Duration Heavy Rainfall Event in Wuhu Based on Multi-Source Observational Data

摘要: 2023年7月19日，安徽芜湖出现一次局地极端短时强降水过程，最大小时雨强达101 mm。利用常规观测、FY-4A卫星、S波段和X波段雷达及ERA5再分析资料，对此次过程的环流背景、中尺度系统演变及热动力结构进行了综合分析。结果表明：此次过程发生在副热带高压边缘高温高湿环境下，高空辐散与低层辐合形成良好垂直耦合，北方冷空气南下触发层结不稳定发展。多个中尺度对流系统(MCS)在发展和合并过程中组织化增强，强降水主要位于TBB低值中心及梯度较大区域。地面“对头风”结构导致近地层暖湿气流强烈辐合，对流系统表现出高质心、中等垂直风切变特征。热动力结构分析表明，低层湿不稳定层结、干冷空气嵌入及正涡度柱发展共同促进了强上升运动和不稳定能量释放，最终导致极端短时强降水发生。研究表明，在高湿厚暖云背景下，即使缺乏典型低空急流条件，MCS合并及边界层辐合仍可造成局地极端短时强降水。

Abstract: On 19 July 2023, an extreme short-duration heavy rainfall event occurred in Wuhu, Anhui Province, with a maximum hourly precipitation of 101 mm. Using conventional observations, FY-4A satellite data, S-band and X-band radar data, and ERA5 reanalysis data, the synoptic background, mesoscale system evolution, and thermodynamic and dynamic structures of this event were comprehensively analyzed. The results show that the event occurred under a hot and humid environment at the edge of the subtropical high, where upper-level divergence and low-level convergence formed a favorable vertical coupling structure, while the southward intrusion of cold air enhanced atmospheric instability. Multiple mesoscale convective systems (MCSs) developed and merged, leading to enhanced convective organization, and the heavy rainfall was mainly located in regions with low TBB centers and large TBB gradients. A surface head-on wind pattern caused strong low-level moisture convergence, and the convective system exhibited characteristics of a high echo centroid and moderate vertical wind shear. Thermodynamic and dynamic analyses indicate that the combined effects of low-level moist instability, dry and cold air intrusion, and the development of a positive vorticity column promoted strong upward motion and the release of unstable energy, ultimately resulting in the extreme short-duration heavy rainfall. The study suggests that under conditions of high humidity and deep warm clouds, extreme short-duration heavy rainfall can still occur through MCS merging and boundary-layer convergence even without a typical low-level jet.