2007年梅雨锋降水的大尺度特征分析

Large-scale Features of the Mei-Yu Front Associated with Heavy Rainfall in 2007

2007年6—7月在华南、长江中下游以及淮河流域先后出现东西走向静止锋暴雨,引起粤东和淮河流域洪涝灾害。分析了这3个地区静止锋暴雨的动力学、热力学结构的异同点。2007年7月引起淮河洪涝的主要强降水是7月8—9日的暴雨,分析了引起这场强暴雨的大气环流特征以及梅雨锋深厚的锋生过程和气旋生成过程。主要结论为:(1)华南前汛期降水、长江梅雨期降水以及淮河强降水出现时东西向静止锋在动力学和热力学的结构相同,可通称为"梅雨锋"。(2)2007年淮河静止锋暴雨的出现,是由于中国东部上空有深厚高空槽发展,诱导梅雨锋上气旋生成过程和深厚的锋生过程。气旋生成过程和锋生过程使梅雨锋上出现强烈的上升运动,形成了致洪暴雨。

The large scale features of the Mei-Yu front associated with heavy rainfall along the Pearl River valley in South China, the Yangtze River valley and the Huai River valley in 2007 are discussed. During the period 1-16 June, the Mei-Yu front extended along Pearl River valley with intense rainfall. In the middle of June with the first westward extension of the subtropical anticy- clone in the West Pacific, the Mei-Yu front jumped to the Yangtze River where it lasted for nine days. With the second westward extension of the subtropical anticyclone in the end of June, the Mei-Yu front jumped to the Huai River valley, where it lasted for two weeks and brought about severe floods with great damages. The dynamical and thermodynamic characteristics of the Mei-Yu front in the three valleys are compared. It is found that the dynamical and thermodynamic struc- tures are all the same and we suggest to use the same ＂Mei-Yu front＂ for the three valleys. During middle of July there was a disastrous flood in the Huai river valley. The mechanism of the torrential rainfall that brings about the severe flood is discussed in the second part. It is found that with the intense development of ridge and trough system along the subtropical jet stream in North China, there was an intense development of a deep trough along 110°E, which induced the development cyclone-genesis and front-genesis in the Mei-Yu frontal zone from 1000-400hPa. With the development of the cyclone-genesis and front-genesis along the Mei-Yu front, there was rapid upward motion along the front zone causing intense rainfall along the Mei-Yu front.