0604号强热带风暴碧利斯对云南的影响及维持机制

The Maintaining Mechanism of 0604 Severe Tropical Storm Bilis and It’s Influence on Yunnan Province

应用MICAPS资料及FY-2C卫星云图,通过天气分析与诊断分析,探讨了0604号强热带风暴碧利斯路径西偏南的原因,对造成云南的暴雨过程进行了分析并研究了这次登陆强热带风暴长久维持不消的物理机制。结果表明:黄海副高南落加强西伸与大陆高压合并加强,高压南侧东北风的牵引作用,是"碧利斯"路径西偏南的主要原因;"碧利斯"造成的云南强降水落区分布在热带低压倒槽前东北风急流区内水汽辐合中心区域,并且与700hPa湿Q矢量辐合区对应较好,热带低压影响期间,大气曾具有湿中性垂直运动结构,具备有利于暴雨系统发展的环境条件;"碧利斯"登陆后长时间和一支深厚的西南急流保持联结,是其长久维持不消的主要因素。西南季风云系卷入热带低压,增强了热带低压的水汽和能量输入,是热带低压得以长久维持并造成云南强降水的另一重要原因。南亚高压在热带低压活动期间增强,高层辐散场的增强,低层辐合、高层辐散的结构,与西南急流相联系的垂直正涡度的维持,有利于热带低压的维持,登陆后的热带低压有向高空强辐散区方向移动的趋势。

MICAPS data was used to research the reasons of the path＇s deflecting south-westwards of 0604 severe tropical storm by synoptic and diagnosis analysis, and by the analysis on the storm rainfall caused by the severe tropical storm in Yunnan Province. The physical mechanism of the maintenance of the tropical storm＇s strength after landfall is also discussed. The result indicates that the main reason of the path＇ s deflecting south-westwards of Bills was the leading of northeast wind at the south of high which was formed by the merging of continental high and the Huanghai subtropical high after its moving southwards and strengthening eastwards. Heavy precipitation caused by Bills happened at the center of water vapor convergence area which located in the northeast jet region on the front of inverted trough of tropical depression, and the location of the precipitation is corresponding better to the wet Q vector convergence area. During the period when the influence of tropical depression existed, the atmosphere had wet neutral vertical moving structure and the situation was beneficial for the growth of storm rainfall system. The interaction between Bills and severe southwest jet for a long time after the landfall of Bills was the main reason for its maintenance. With the fading of southwest jet, the precipitation finished completely. The southwest monsoon cloud＇s getting into the tropical depression strengthened the input of water vapor and energy, which was another important reason that maintained the tropical depression and caused the heavy precipitation. The South Asia high strengthened during active period of the tropical depression, and the strengthening of divergence field on the upper level, the existence of lower level convergence and upper level divergence, and the maintenance of vertical positive vorticity which was related with southwest jet were beneficial for the maintaining of the tropical depression and the movement tendency of the tropical depression to upper severe divergence area after its landfall.