一次西南涡诱生气旋引发的湖南大暴雨个例分析  

A Case Study of a Heavy Rainstorm in Hunan Triggered by the Induced Cyclone of Southwest Vortex

作　　者：刘金卿 李子良 LIU Jinqing;LI Ziliang(Hunan Meteorological Observatory,Hunan,Changsha 410118,Hunan,China;College of Oceanic and Atmospheric Sciences,Ocean University of China,Qingdao 266100,Shandong,China)

机构地区：[1]湖南省气象台,湖南长沙410118 [2]中国海洋大学海洋与大气学院,山东青岛266100

出　　处：《高原气象》2020年第2期311-320,共10页Plateau Meteorology

基　　金：国家重大科学研究计划项目(2015CB953900);国家自然科学基金项目(41176005);中国气象局气象预报业务关键技术发展专项[YBGJXM(2017)1A-10,YBGJXM(2018)1A-10]。

摘　　要：基于NCEP再分析资料、常规观测站点降水数据,研究了2013年5月14-15日发生的一次西南涡诱生气旋的结构演变特征及其在湖南产生大暴雨的动力学机理,最后利用Okubo-Weiss参数(OW)及位势涡度(Potential Vorticity,PV)定量分析了西南涡切变线和诱生气旋的发展过程。结果表明:(1)此次大暴雨是一例由西南涡诱生气旋引发的强降水过程。在气旋波生成阶段,西南涡风场由对称结构变成不对称结构;在诱生气旋的成熟阶段,西南涡风场再次发展为对称结构。切变线上的不稳定为气旋性扰动的生成提供了有利环境条件,导致西南涡诱生气旋波沿切变线东移并随之产生大暴雨。(2)在气旋波生成之前,西南涡环流及西风绕流涡度带表现为OW参数和PV大值区,西南涡外围是OW参数负值环绕区,有利于切变线的生成和维持。在绕流涡度带与切变线结合之后,切变线的旋转性加强,风场的旋转性诱生出气旋性扰动。(3)诱生气旋发展的主要原因是气旋波在有利的高低空形势场配置下不断积累正位涡,OW极大值和PV极大值重合并远超停滞的西南涡。Based on the NCEP reanalysis data and the conventional station precipitation data,the structural evolution features and the dynamic mechanism of the large-scale heavy rainstorm in Hunan Province of the induced cyclone of a Southwest Vortex(SWV)that took place from 14 to 15 May 2013 were studied,and the Okubo-Weiss(OW)parameter and the Potential Vorticity(PV)were used to analyze the development of the shear line and the induced cyclone of SWV.The results show that:(1)The strong precipitation in Hunan Province was a typical heavy rainstorm process triggered by the induced cyclone of SWV.At the generation stage of the cyclone wave,the SWV wind field changed from a symmetrical structure to an asymmetric structure.At the maturity stage of the induced cyclone,the SWV wind field developed into a symmetrical structure again.The instability on the horizontal shear line provided favorable environmental conditions for the generation of cyclonic disturbances,which caused the cyclone wave induced by SWV to move eastward along the horizontal wind shear and produce a heavy rainstorm.(2)Before the cyclone wave was generated,the SWV and the vorticity band of the westerly flow were shown as the OW parameter and the PV large value area,and the periphery of SWV was a surrounding negative-value area of the OW parameter,which was conducive to the generation and stability of the shear line.After the vorticity band was combined with the wind shear,the rotation of shear line is enhanced,and the rotation of the wind field induced cyclonic disturbance.(3)The main reason for the development of the induced vortex was that the cyclone wave accumulated positive vorticity under the favorable high and low altitude situations,and the area of OW maxima and the area of PV maxima overlapped to exceed the stagnant SWV.

关 键 词：西南涡 气旋波 诱生气旋 Okubo-Weiss参数 位势涡度 

分 类 号：P458[天文地球—大气科学及气象学]