“05·6”华南持续性暴雨的成因分析

ANALYZING CONTINUOUS RAINSTORM IN SOUTHERN CHINA IN JUNE 2005

2005年6月华南出现大范围持续性暴雨过程,造成巨大损失。利用常规气象资料、卫星云图TBB资料及T213分析场资料,对此次持续性暴雨过程的成因进行了分析,结果发现:这次暴雨过程充足稳定的水汽主要源自印度洋,这与“94.6”等以往华南暴雨水汽主要来自于南海不同。高低空急流与切变线是这次强降雨过程的触发系统,低空急流输送了丰沛的暖湿空气,维持了低空对流不稳定形势。冷暖气流在切变线南侧、低空急流左侧交汇,产生强烈辐合上升运动,触发了强降水。对流云系上MCS的不断生消是造成强降雨持续的直接原因。本次过程存在一次高空急流的变化,高空由西北急流转为西南急流,切变线的变化趋势与这一变化过程相呼应;这一特征也是暴雨过程得以维持的重要原因。

A wide-range continuous rainstorm process occurred in southern China in June, 2005, and led to severe flood, landslide and caused great damages in the region. This paper makes the diagnostic analysis of the rainstorm process by using conventional meteorological date, satellite cloud images, TBB and data of T213 analysis field, and finds： The sufficient and stable vapor of the rainstorm process mainly originates from the Indian Ocean, which is different from the previous ones coming from the South China Sea such as the June 1994 rainstorm. The high and low level jet streams and shear line are the triggering system. The low-level jet stream maintains convectively unstable situation on low levels. The upper one supports symmetric unsteady condition on upper levels. The cold and warm currents meet at the southern side of the shear line and the left side of the low-level jet stream to produce an upward movement of intensive convergence and trigger the rainstorm. The direct reason of the sustained rainstorm is that MCS kept growing and decaying in the convective clouds. There was a change of high-level jet stream in which the direction of high altitude jet stream turned to southwest from northwest, and the change tendency of the shear line was corresponding with it. This characteristic is also an important reason that the rainstorm process could maintain.