一次梅雨暴雨过程的双峰结构分析

Dual-front Structure Analysis of one Meiyu Rainstorm Process

对2007年7月7～9日的一次梅雨暴雨的分析，发现这次暴雨与梅雨期间的双锋面结构有关。在暴雨区的两侧由于梅雨锋与副热带锋共同作用，形成了典型的双锋面结构，梅雨双锋的出现使暴雨强度大大加强。分析表明，此次降水过程的双锋结构经历了4个阶段的演变过程，通过湿位涡分析发现双锋结构可导致倾斜涡度发展使中低层涡度加大，有利于降水发展。在各种类型的暴雨过程中在副热带锋区和梅雨锋区均有倾斜涡度发展，S形态的双锋结构两类锋区的共同作用不明显，但其他类的双锋结构则有两支锋区的共同作用。

Basing the Meiyu rainstorm process on 7-9 July 2007, the relations between the rainstorm and the dual-front structure during the rainy season were discussed. Results show that the dual-front structure is formed by the combined effect from the Meiyu front and sub-tropical front on the both sides of the rainstorm district, which enhances the rainstorm. The dual-front structure in this precipitation process has undergone four stages of the evolution. The analysis of moist potential vorticity shows that the dual-front structure can lead to the development of slantwise vorticity in increasing low-level vorticity, which is conducive rainfall. Slantwise vorticity is usually developing in the sub-tropical front areas and Meiyu front district during various types of rainstorm processes. Almost all types of dual-front structures have an obvious combined effect between the two front zones, except for ＂S form＂ type.