广西“3.25”暖区强对流雷达回波特征及成因分析

Analysis of radar features and formation of ‘3.25’ warm sector severe convection weather process in Guangxi province

摘要:

本文利用多源观测数据和再分析资料，对2020年3月25日发生在广西的一次强对流天气过程进行了综合分析，结果表明：（1）本次过程是在500hPa高空冷槽东移叠加低层偏南暖湿气流加强的天气背景下发生的，是典型的暖区强对流。（2）过程中先后形成两条飑线和一个超级单体，且两条飑线路径相似；第一条飑线具有低质心的暖云强降水特点；第二条飑线前沿反射率因子梯度高，后侧入流及动量下传特征明显；超级单体在桂东南一带造成降雹。（3）在对流触发时段，越南北部上空850hPa为暖平流，其上500hPa叠置冷平流，维持较长时间，形成了持续的强不稳定区，两条飑线的初始对流在强不稳定区中由地面辐合线触发；飑线发展和维持的主要机制是近地面冷池出流与低层环境风场的相互作用。

Abstract:

A regional severe thunderstorm on March 25, 2020 in Guangxi province was investigated based on multi-source observations and reanalysis data. The results are as follows. (1)The severe thunderstorm occurred in a warm area, and the trough at 500hPa and low-level south jet provided favorable conditions for the formation of the thunderstorm. (2)The severe thunderstorm was caused by two bow echoes and a super cell. The first squall line had the characteristics of a low barycenter in warm cloud. The reflectivity gradient of the front of the second squall line was high, and the second squall line had characteristics of front inflow and momentum downward. The super cell led to hail in southeast of Guangxi.(3) The cold advection was superimposed with the warm advection over northern Vietnam, forming a persistent strong unstable zone, where two squall lines were triggered by surface convergence lines. The main mechanism for the development and maintenance of squall lines was the interaction between the cold pool outflow and low-level environmental wind fields.