广西区域极端特大暴雨成因个例分析

Causal Analysis of a Regional Extreme Severe Rainstorm in Guangxi

利用常规观测资料、FY-2E卫星观测资料、雷达探测资料以及自动站雨量资料等,对2010年6月28日广西极端特大暴雨过程进行分析;结果表明:①暴雨灾害具有区域小、降雨时段集中、过程雨量大、短历时降雨强及引发次生灾害特别重等特点;②亚欧中高纬度500hPa呈两脊一槽型、200hPa南亚高压脊线贯穿广西上空及西南季风活跃是暴雨的环流背景;高空低涡、地面干线是主要天气系统配置,属低涡暴雨型;③强不稳定能量及层结的存在、850hPa以下低层辐合、700hPa附近明显涡旋、整层大气上升运动、850hPa以下层高湿及水汽强烈辐合是主要物理量特征;④中尺度低压、低涡及气流辐合等是中尺度对流触发条件。FY-2E红外云图上对流云团生成、合并对强降雨有重要指示意义,暴雨发生在云团合并发展阶段,FY-2E的TBB值小于200K可以作为短历时强降雨的指标。低质心雷达回波产生的列车效应和地形作用是造成强降雨的重要因素,低层辐合、高层辐散导致的强烈上升运动,有利于强对流的发展与维持。

By using the conventional observation, FY-2E satellite, radar detection, and automatic weather station rainfall data, the extreme severe rainstorm on 28 June 2010 in Guangxi is analyzed. The results show： （1） The rainstorm disaster has the features of small influencing area, concentrated in time, large process rainfall, short duration, and serious secondary disaster. （2） The rainstorm occurred in the circulation pattern of ＂two ridges and one trough＂ over the high-latitude Eurasia at 500 hPa, with the ridge line of South Asia High throughout Guangxi at 200 hPa accompanying with active southwest monsoon. Configuration of the upper vortex and surface dry line indicates a vortex-type storm. （3） The main physical-quantity characteristics included the presence of strong instability energy and stratification, low- level convergence at 850 hPa and below, obvious vortex near 700 hPa, upward motion in the whole atmosphere, and high humidity and strong convergence of water vapor at 850 hPa and below. （4） Mesoscale !ow, vortex, convergence of airflow, etc., triggered the mesoscale convection. Formation and mergence of convective cloud clusters on the FY-2E satellite cloud picture has implications for heavy rainfall. The rainstorm occurring in the development stage of clouds and TBB value being less than 200 K could be used as an indicator of short-term heavy rainfall. The train effect produced by the low-centroid radar echoes and the effect of topography are important factors in causing heavy rainfall. Strong vertical motion induced by the low-level convergence and upper-level divergence is conducive to the development and maintenance of strong convection.