皖南初春平行线状对流系统引发的大暴雨分析

Analysis of Heavy Rainstorm Caused by Parallel Linear Convection System in Early Spring in Southern Anhui

利用多源气象观测资料和欧洲中心ERA5再分析资料研究2022年3月中旬安徽南部的一次大暴雨过程。结果表明:受稳定的贝湖东部低槽、西北太平洋副热带高压与东移加强的华西疏散槽共同影响,地面冷锋快速南下,引发大暴雨的中尺度平行线状对流系统形成于地面冷锋附近大别山区南部迎风坡上并向东移动,呈现出列车效应。对流层中低层西南急流、低涡切变、大的垂直风切变为其发展、维持提供了有利的环境条件;复杂地形对平行线状对流系统的发展演变具有重要作用,山地增强了南北水平温度梯度,并通过迎风坡或喇叭口的近地面风场辐合不断产生新的上升气流,低层对流触发后不断随着偏南气流北移,形成线状对流系统,呈现出后向传播特征;整个平行线状对流随着中层引导风向偏东方向移动,强降水中心太湖不仅有东南风与北侧绕大别山区南下的东北风辐合,且处于迎风坡的喇叭口,地形抬升加强辐合作用,对流发展最为旺盛;双偏振雷达参量和雨滴谱仪显示,太湖上空为粒子数密度大的大雨滴,降水效率高。

A heavy rainstorm process in the south of Anhui Province in mid-March 2022 was studied using multi-source meteorological data and ERA5 reanalysis data from the European Center.The results showed that under the influence of the stable east Bay Lake trough,the Northwest Pacific subtropical high and the eastward strengthening West China evacuation trough,the surface cold front moved southward rapidly,and the mesoscale parallel linear convective system that caused heavy rain formed on the southern windward slope of Dabie Mountain near the surface cold front and moved eastward,showing a train effect.The southwest jet,low vortex shear and large vertical wind shear in the middle and lower troposphere provide favorable environmental conditions for its development and maintenance.The complex terrain played an important role in the development and evolution of parallel linear convective system.The mountainous area enhanced the north-south horizontal temperature gradient and continuously generates new updrafts through the convergence of the near-surface wind field on the windward slope or the bell-mouth.After the triggering of the low-level convection,the linear convective system moved northward with the southerly air and presents the characteristics of backward propagation.The whole parallel linear convection moved eastward with the mid-level guiding wind direction.The center of heavy precipitation in Taihu Lake not only had the convergence of the southeast wind and the southward northeast wind around Dabie Mountain,but also was located at the bell-mouth of the windward slope.The topographic uplift enhanced the cooperation of the radiation,and the convection developed the most vigorously.The dual-polarization radar parameters and raindrop spectrometer showed that there were a large number of dense raindrops over Taihu Lake,and the precipitation efficiency was high.