2009年6月一次飑线过程灾害性大风的形成机制  

The Formation Mechanism of Damaging Surface Wind during the Squall Line in June 2009

作　　者：梁建宇[1,2] 孙建华[1] 

机构地区：[1]中国科学院大气物理研究所,北京100029 [2]中国科学院研究生院,北京100049

出　　处：《大气科学》2012年第2期316-336,共21页Chinese Journal of Atmospheric Sciences

基　　金：国家自然科学基金项目41075032;中国气象局公益类行业专项GYHY200906004;国家重点基础研究规划项目2010CB951804

摘　　要：对2009年6月3～4日一次产生地面大风的人字形强飑线过程进行了观测资料分析和数值模拟研究。观测资料的分析表明:人字形回波系统的右半支的结构与一般的飑线系统类似,在系统成熟阶段地面存在明显的雷暴高压、冷池、出流边界、尾流低压等特征;人字形回波的左半支对应的地面风速比右半分支弱,且强对流区后部没有对应层状云、地面雷暴高压、冷池等;灾害性大风的产生主要由这个人字形系统的右半支造成的。高分辨率模拟结果的分析表明:系统由线状转变为人字形系统的原因是由于气旋扰动的冷暖切变的作用,冷、暖切变上分别形成了有层状云和无层状云的飑线分支。系统的右半分支在发展阶段和成熟阶段对流区有比较强烈的下沉气流,系统的后部的中层入流可能会加强这个下沉气流。中层入流是地面大风形成的重要原因之一;成熟阶段垂直于飑线系统主要有三股气流,包括从飑线前部向后的入流和中层从后部到前部的入流,以及前部的低层入流到高层的出流。A severe occlusion type of squall line is investigated by using observational data analysis and WRF model simulation, which occurred in Henan Province in China on June 3, 2009 and produced surface damaging high wind. The observational data analysis result shows that： The right branch of this system has some similar features to typical squall lines. Some features such as thunderstorm high, boundary outflow, cold pool, and wake depression are presented in the mature stage. By contrast, for the right branch there are not significant features such as stratiform cloud, thunderstorm high, and cold pool in the left branch of the squall line. The surface wind within the region of left branch is weaker than that in the right branch. High wind was mainly caused by the right branch of the system. High-resolution model outputs reveal that the formation of occlusion morphology of this system is caused by cold wind shear and warm wind shear near the ground. These shears lead to the existence of right branch with stratiform cloud and left branch without stratiform cloud, respectively. Furthermore, the formation mechanism of the surface high wind and the organization mode of the right branch of this system in the mature stage have been revealed： The downward motion of the convective region in the right branch is intense in developing and mature stage. Rear inflow in the middle troposphere may intensify such downward motion. Rear inflow is an important factor for surface high wind. There are three major air flows within the cross section of the right branch, including front-to-rear inflow in front of the squall line, rear-to-front inflow in the middle layer, and inflow in the lower layer which changes to outflow in the high layer.

关 键 词：飑线 地面大风 人字形回波 中层入流 

分 类 号：P445[天文地球—大气科学及气象学]