台风麦莎（Matsa）特大暴雨及其结构特征分析

利用自动站资料、雷达观测资料、NECP1°×1°再分析资料,采用相对于台风中心的移动坐标合成分析方法以及WRF模式的诊断分析,对2005年8月登陆浙江造成历史罕见特大暴雨的台风麦莎(Matsa)降水量分布特征进行分析,讨论与特大暴雨有关的台风结构变异。结果表明:①台风麦莎影响期间降水量的分布与通常热带气旋以螺旋雨带结构为主要特征的风雨分布特征显著不同,台风麦莎(Matsa)系统的右前、右后(第1、第2)象限出现了结构显著变异,对台风特大暴雨的特征落区分布有明显影响。②雷达与自动气象站资料分析揭示,在台风第1和第2象限发现有多个雨团重复生成和移动,它们与雷达回波观测到的强弱相间的中尺度上升和下沉气流相间区域相对应,是中尺度"降水细胞"频繁再生与移动的强烈发展区,对构成台风特大暴雨和灾害起重要作用。③具有再生能力的"暴雨细胞"特征结构的强烈发展区域出现动能的显著聚集,有利于台风中水汽在该区域的抽吸。台风系统的局部出现这样结构变异特征,对台风强降水落区的监测预报有重要指示意义。

Severe Heavy Rainfall and Unusual Structure of Typhoon Matsa

By using the data from AWS stations, radar observations, re-analysed data of NCEP 1°×1°, adopting the relative coordinate system with Matsa moving, a case study is made of the abnormal rainstorm process for typhoon Matsa in August 2005. The results indicate： （1） The structure of typhoon Matsa is quite different from common typhoons, and the unusual distribution of rainfall is closely related with the special situation. （2） There was a number of rain clusters reproduced and moved in the first and second quadrant of the typhoon system, which were corresponding to the areas where there were strong-weak interweaved radar echoes for updrafts and downdrafts occurred alternately; the frequent appearing and movement of mesoscale ＂rain cells＂ were key mechanisms for the generation of the severe rainstorm. （3） The areas where local unusual variability occurred due to special structure changes in certain quadrants of the typhoon system can be a significant indicator for the monitoring and forecasting of typhoon heavy rainfall.