1621秋季台风“莎莉嘉”路径突变和暴雨成因分析

Diagnostic analysis of the sudden change in the autumn typhoon “Sarika” track and its rainstorm in Guangxi

用常规观测资料、卫星云图资料、流场资料和各种物理量诊断综合分析"莎莉嘉"后期路径突变和形成暴雨的各种有利因素。结果表明:(1)台风"莎莉嘉"后期路径在北部湾突然转折,这主要是由副高的变化引起,台风云系与锋面云系相联系,转受西风带系统引导;(2)这次台风暴雨在广西分布不均匀,分别包含了台风本体暴雨、台风与冷空气相互作用的暴雨、台风和地形作用产生的暴雨;(3)这次暴雨过程中有充足的水汽输送和强烈的水汽辐合,强烈的上升运动是形成暴雨的直接动力条件,局地特大暴雨与地形的增幅作用有重要关系。

The autumn typhoon ＂Sarika＂ was the strongest landfall typhoon in Guangxi in October since 1949. ＂Sarika＂ attacked Guangxi directly, inducing a large-scale rainstorm and a strong wind. The track of ＂Sarika＂ sudden changed over the Beibu Gulf when at the end of its life cycle, but none of the numerical models predicted the sudden change successfully, leading to a large bias in precipitation prediction and a hardly ideal forecast service. This paper focus on the sudden change of typhoon track and the typhoon rain- storm based on various observation data, satellite cloud images, wind fields, and physical quantityfields analysis. It was found that the changes of Western-Pacific Subtropical High, South Asian High, and the up- per-level jet stream were beneficial to the connection between the typhoon and the front cloud systems, and the typhoon steering current turned to the west, resulting in the sudden change of the typhoon track. This large-scale typhoon rainstorm had an uneven distribution in Guangxi, which was caused by the typhoon, cold air, and orographic lifting effect. There were an abundant water vapor supply and a strong moisture convergence during the rainstorm and it was directly stimulated by the strongly upward motion. Besides, the local extraordinary rainstorm had a close connection with the amplifying effect of the terrain.