华南暴雨中尺度对流系统的形成及湿位涡分析  

Moist Potential Vorticity Analysis of the Heavy Rainfall and Mesoscale Convective Systems in South China

作　　者：蒙伟光[1] 王安宇[1] 李江南[1] 冯瑞权[1] 侯尔滨[2] 

机构地区：[1]中山大学大气科学系 [2]澳门地球物理暨气象台

出　　处：《大气科学》2004年第3期330-341,共12页Chinese Journal of Atmospheric Sciences

基　　金：国家重点基础研究发展规划项目G1 9980 40 90 0;中国科学院知识工程重要方向项目ZKCX2 SW 2 1 0资助

摘　　要：利用MM5模式对发生在 1 998年 5月 2 3～ 2 4日华南暴雨和中尺度对流系统(MesoscaleConvectiveSystem ,简称MCS)模拟的模式输出资料 ,根据湿位涡守恒原理和倾斜涡度发展理论分析了暴雨和MCS形成和发展的原因。结果表明 ,暴雨和MCS发生在倾斜湿等熵面具有弱对流稳定性的下陷区 ,沿湿等熵面下滑的冷空气与倾斜上升并具有较强对流有效位能的暖湿空气在下陷区会合的过程中经历了对流稳定性减小的过程 ,导致暴雨和MCS发生发展区域有气旋性的涡旋发展。对流发展区域的上空满足条件对称不稳定发生的条件 ,MCS中上升气流呈倾斜状态。由于湿等熵面倾斜 ,在暴雨和MCS的发展过程中 ,水平风垂直切变和湿斜压度的增大也有利于涡旋的发展 ,使暴雨和MCS得以维持。最后 ,给出了华南地区湿等熵面上暴雨和MCS发生发展的一个物理概念模型。By using the MM5 model outputs of a successful numerical simulation on a South China heavy rainfall event and the mesoscale convective system (MCS) occurred during 23～24 May 1998, the development of the heavy rainfall and MCS have been investigated in terms of moist potential vorticity principle and slantwise vorticity development theory The results show that, on the slantwise moist isentropic surface, areas with high pressure and positive moist potential vorticity are favorable for the development of heavy rainfall and MCS As the cold air slide down along the moist isentropic surface and confluence with the slantwise upward motion warm and moist air with high convective available potential energy values, both of them experience a stability decreasing process, and lead to cyclonic vorticity development Over deep convection area, the atmosphere exhibits the signature of conditional symmetric instability, and MCS is characterized by slantwise upward motion As for the slantwise of moist isentropic surface, the increase in vertical shear of horizontal wind or enhancement in moist baroclinity also resulted in the increase of vertical vorticity and the development of MCS Finally in the article, a physical conceptual model about the development of heavy rainfall and MCS over South China was presented

关 键 词：暴雨过程分析 湿位涡 对称不稳定 中尺度对流系统 华南暴雨 数值模拟 

分 类 号：P458.121.1[天文地球—大气科学及气象学]