发生在中国大陆的台风变性加强过程分析

ANALYSIS OF THE EXTRATROPICAL TRANSITION OF TROPICAL CYCLONE OVER MAINLAND OF CHINA

通过对登陆台风Winnie(1997)的演变过程分析,发现登陆后的台风经历三个阶段:衰减阶段、变性阶段、重新加强阶段。其变性过程类似于Sekioka等人提出的复合型,变性后逐渐演变为Shapiro-Keyser气旋模型。通过对物理量的诊断分析发现,对流层中高层冷空气的下沉入侵以及对流层低层的暖平流是热带气旋变性的原因。冷空气的入侵使具有暖心结构的热带气旋演变为斜压结构的温带气旋。变性后气旋得到了重新发展,低层维持的较明显暖平流以及与高空急流相对应的散度区和高空涡度平流是导致气旋重新发展的重要物理因子。

Typhoon Winnie(1997) experienced three stages after its landfall on China:weakening, transformation, and re-intensification. The characteristic of transformation is similar to the complex transition model proposed by Matano and Sekioka. During the re-intensification stage, the transformed cyclone developed into a pattern of Shapiro-Keyser Cyclone model. From the diagnosis we can find that the cause of Winnies transformation is the intrusion of cold air from the middle-upper troposphere and the warm temperature advection in the lower. Winnie redeveloped after transformation, which is the result of three vital factors: the warm temperature advection in the lower troposphere, the divergence located on the right side of the entry of upper jet and the cyclonic vorticity advection in the upper.