“达维”(2005)台风经过海南岛过程非对称降水的成因分析

ANALYSIS OF CAUSATION OF ASYMMETRIC PRECIPITATION ASSOCIATED WITH STRONG TYPHOON "DAMREY"

2005年9月25日08时—27日08时,强台风"达维"从海南岛中部陆地经过的48小时期间,给海南岛带来一次强降水,表现出海南岛南侧降水大于北侧的非对称特征。利用热带测雨雷达资料(TRMM)对这次非对称降水的中尺度特征进行分析,并从次天气尺度系统扰动、垂直风切变、地形作用等方面对其成因进行探讨。结果表明:⑴次天气尺度扰动系统为中尺度雨团、中尺度雨带的形成提供了有利的动力条件;⑵垂直风切变下风方向左侧有利于对流发展的区域始终位于海南岛南部,导致降水出现非对称特征;⑶海南岛山脉地形通过刺激小对流单体的形成与合并发展,从而促进中尺度降水系统形成,最终致使海南岛南部暴雨增幅。

Severe typhoon Damrey moved across Hainan Island from 0800 LT 25 Sept. to 0700 LT 28 Sept. in 2005, and gave rise to a significant rain process during 48h. The precipitation intensity on the southern Hainan Island is stronger than that on the northern, showing obvious asymmetric distribution. Using Tropical Rainfall Measuring Mission （TRMM） data, the associated mesoscale characteristics of the precipitation were analyzed, and the formation of asymmetric rainfall distribution was investigated in the context of a subsynoptic scale disturbance, vertical wind shear and orographic factors. The results are shown as follows. （1） The subsynoptic scale system provided favorable dynamic conditions to the genesis of mesoscale rain clusters and rainbands. （2） The southern Hainan Island was located to the left of the leeside of the shear all the time, being favorable to the development of convection and leading to the asymmetric rainfall distribution. （3） Mountain terrain in the southern Hainan Island stimulated the genesis and combination and development of convective cells, promoting the formation of mesoscale precipitation systems and ultimately resulting in rainfall increase in the southern island.