干侵入对我国东部一次强飑线过程的作用分析

利用常规观测资料、地面加密观测资料和多普勒雷达等多种资料，分析2018年5月27日广西飑线过程的天气背景、环境条件、发展机制及大风的成因，结果表明：500 hPa冷舌叠加低层暖脊建立了较强的层结不稳定结构，同时环境具有较大的对流有效位能，为飑线的生成和发展提供有利的环境条件；广西沿海中尺度辐合线是导致此次飑线系统初始对流形成的触发机制；飑线低层暖湿入流到风暴顶形成辐散，中层后侧干冷空气入流使得飑线内下沉气流加强，下沉气流出流在风暴前侧形成辐合，触发新的对流，以及入流和出流错开形成飑线系统的自组织结构，使得飑线在弱垂直风切变条件下发展维持；近地面冷池的合并加强，造成的冷池密度流是大风形成的主要原因。

A theory for strong long-lived squall lines

Based on conventional observation data, automatic weather station data and CINRAD-SA Doppler radar data, we analyzed the weather background, environmental conditions, development mechanism and the gale that caused for the squall line event on 27 May 2018 in Guangxi. Results show that the cold tongue at 500hPa superimposed with the warm ridge in the lower layer built a strong stratification instability structure, with a high value of CAPE, which provided a favorable environment for the development of the squall line. The mesoscale convergence line located at the coast of Guangxi was the trigger mechanism for the initial convection system that finally leaded to the formation of the squall line system. The warm and moist inflow from the lower layer of the squall line reached the top of the storm and diverged. The cold and dry air inflow from the rear of the middle layer strengthened the downdraft within the squall line. The downdraft outflow formed convergence on the front side of the storm to trigger new convection. The self-organization structure of the squall line was formed by the inflow and outflow stagger. These were the important reasons for maintenance and development of the squall line under the condition of weak vertical wind shear. The main reason of strong wind was the density current caused by the merger and strengthening of surface cold pools.