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
出处
《大气科学》
CSCD
北大核心
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
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
moist potential vorticity
conditional symmetric instability
mesoscale convective system
South China
heavy rainfall
numerical simulation
