热带气旋中的一部分在进入中纬度地区后会发生变性.变性过程通常会产生暴雨和强风,对人类在海区和陆地上的安全造成严重威胁.通过对变性过程的大量的研究,目前已经对此过程的理解逐步深化.基于对相关研究的综述,介绍了变性的定义和以“相空间”为代表的一些定量的分类方法.对冷空气、锋生过程以及西风带高空槽和地面斜压区等系统与热带气旋相互作用在气旋变性过程中所起的作用进行了讨论.对变性过程中的降水分布规律、风场特征的演变和中纬度环流受到的影响也作了专门分析.最后,初步给出了未来研究该区域热带气旋变性问题的方向的一些建议.
A number of the tropical cyclones(TC) near the coast of China sometimes underwent a process of extratropical transition(ET). It can frequently produce intense rainfall and strong winds which seriously threatening to land and maritime activities. In this paper a brief review of the current understanding of the process involved in ET is presented. Definition of ET is described and a set of the qualitative classification methods such as "phase space method" is introduced. The mechanism of ET is documented by the discussion of the roles playing respectively by cold air mass aloft, frontgenisis and the interaction between TC and westerlies synoptic features including troughs at middle to upper troposphere and baroclinic zone at surface. The characteristics of torrential precipitation with ET are analyzed while impacts of TCs undergoing ET on extratropical wind field and circulations are also investigated.Finally, some suggestions for the future directions for research into ET of the TCs near the China coast are given.