长三角盛夏—初秋强降水的延伸期过程预报探析

Exploration of forecast for heavy rainfall in extended period over Yangtze river region

针对长三角汛期强降水过程,根据不同降水类型的特性,提出分时段建立低频模型并给出建模流程。综合分析长三角汛期强降水期的低频特性,将低频气旋及反气旋区分划分7个关键区。重点研究盛夏—初秋时段的强降水特征,在总结强降水期低频特征的基础上,借助EOF分解建立延伸期大—暴雨的预报模型:1区或2区有低频气旋维持并发展;6区、7区或5区存在低频反气旋。并且在7个关键区中1、2区的低频气旋及5、6、7区的低频反气旋为主要低频系统,起决定作用,而3区的低频系统为次要低频系统,起辅助作用。利用该模型提前30 d预报出2012年汛期最强降水过程,并分析本次过程的低频系统演变,给出动态演变模型。

According to the characteristics of different types of rainfall,the low-frequent synoptic map for forecasting model of heavy rainfall in different time period over Yangtze River Delta region was constructed.Based on the comprehensive analysis on the low-frequent characteristics of heavy rainfall over Yangtze River Delta region,the low-frequent cyclone and anticyclone were divided into 7 key zones.Then,the heavy rainfall forecasting model in extended period by Empirical Orthogonal Function（EOF） analysis was established for the midsummer-early autumn period：Zone 1 or Zone 2 was maintained and developed by a low-frequent cyclone; Zone 6,7 or Zone 5 were provided by a low-frequent anticyclone.These five areas have become the main key areas and the above two low-frequency systems were prerequisites for the heavy rainfall.Low-frequency system in Zone 3 and 4 area played a secondary role,so Zone 3 and 4 were defined as a secondary key areas.The key areas played a decisive role in the forecast,while the minor key areas played a reference role.