致洪暴雨过程中尺度涡旋的结构和准平衡特征分析
投稿时间: 2016-04-24  最后修改时间: 2016-08-19  点此下载全文
引用本文:
摘要点击次数: 547
全文下载次数: 307
作者单位E-mail
谭伟才 国防科技大学 气象海洋学院, 江苏 南京 211101;中国人民解放军75839部队, 广东 广州 510510  
钟玮 国防科技大学 气象海洋学院, 江苏 南京 211101 wzhong_vivian@126.com 
陆汉城 国防科技大学 气象海洋学院, 江苏 南京 211101  
李启华 国防科技大学 气象海洋学院, 江苏 南京 211101  
基金项目:国家自然科学基金资助项目(41275002;41175054);国家自然科学基金重点资助项目(41230421)
中文摘要:利用2008年6月广西致洪暴雨过程高分辨率数值模式资料,分析引起暴雨的中尺度涡旋在移动和持续性发展过程中其内部结构的演变以及系统的动力学特征。研究结果表明,中尺度涡旋是导致此次广西暴雨的主要系统,其发展移动过程中伴随有强烈上升运动的深厚湿对流,并在中高层持续形成明显的暖心结构。此次涡旋系统移动过程可分为涡旋南移和涡旋东移两个阶段,由于受到环境场的影响,涡旋中心区域动量、热量和水汽的再分配为其持续性发展提供有利条件。同时诊断分析表明,涡旋内部存在具有继发特征的长时间维持的组织化深厚湿对流系统,以强非地转分量为特征的超地转流,并表现出涡散运动共存且同量级的特征,具有典型的准平衡特征。
中文关键词:暴雨  中尺度涡旋  结构特征  准平衡特征
 
Structure and quasi-balanced feature analyses of the mesoscale vortex during a flash-flood-producing rainstorm process
Abstract:Based on a high resolution numerical simulation of the flash-flooding rainstorm process in Guangxi in June 2008,the evolution of the inner structure and dynamical features of the mesoscale vortex,which caused the heavy rainfall,have been investigated in terms of movement and continued development process.
By means of synoptic analysis,it is found that the mesoscale vortex was the main system leading to the rainstorm in Guangxi.The core of the rain band at different times mainly lied in the eastern part of the vortex within the range of 400 km,and the track and intensity of the rain band coincided with those of the vortex.The structure of the mesoscale vortex was especially distinct on 700 hPa,with the horizontal size ranging from 600 to 900 km.In addition,its move path could be divided into two stages:the southward moving stage and the eastward shifting stage.
Using the high-resolution model output data to analyze the inner subtle dynamic and thermodynamic structures of the mesoscale vortex,it is shown that strong ascending motion existed in the vortex center,which was quite beneficial to the formation of organized deep and moist convection systems.When the vortex reached its intensity peak,the vertical size of these convection systems could run through the entire troposphere,with the rotational motion and potential motion reaching the same magnitude.During the vortex's development process,the release of latent heat showed that there was an obvious warm core at the middle and high levels of the vortex center,and the stronger the vortex grew,the more distinct it became.Meanwhile,upward vertical transportation of warm wet flow,which was caused by strong convergence at low levels,signified that the vortex center attained high humidity.Influenced by the environment in the vortex's movement and development process,the redistribution of momentum,heat and moisture in the vortex center area took place as follows:(1)As the vortex moved southward along the Yunnan-GuizhouPlateau,its central pressure decreased and a uniform horizontal circulation was formed,with multiple strong convective systems evolving at the vortex center and on both sides.(2)As the vortex moved southward and approached the low-level jet(LLJ),the coupling effects of positive vorticity disturbance in the vortex center and positive vorticity shear on the left of the LLJ caused the vorticity to strengthen greatly,thus generating the maximum of vorticity and upward motion near the ground layer,which caused the moist convection and rainfall to both become the strongest in the vortex's center.(3)During the vortex's eastward movement stage,the influence of the LLJ became more important.In the eastern side of the vortex,the air was warm and wet,and possessed more convective instability energy,while stronger vertical movement and convective activity also appeared.Meanwhile,in the west,the air became significantly colder and drier,with almost no vertical movement or convective activity.Analysis of the three-dimensional flow field structure of the mesoscale vortex indicates that there were typical quasi-balanced dynamical features present in the mesoscale vortex,which could be described in detail by successively occurring long-lived organized deep moist convection systems,strong super-geostrophic flow with a large ageostrophic component,as well as intensive divergence which coexisted and had the same magnitude as the strong rotation during its lifetime.
keywords:rainstorm  mesoscale vortex  structural features  quasi-balanced feature
查看全文  查看/发表评论  下载PDF阅读器