一次广东典型龙舟水暴雨过程的扰动形势分析

ANOMALOUS SYNOPTIC PATTERN OF TYPICAL DRAGON BOAT PRECIPITATION PROCESS IN GUANGDONG PROVINCE

“龙舟水”期间的极端降水,常以近似平行的多条雨带出现,过量的降水会造成流域的或大范围的洪涝灾害。分解大气中的基本变量为瞬变气候与瞬时扰动两个部分,用后者揭示龙舟水期间强降水的区域分布特征。2020年6月5—9日出现在广东省中部和北部地区的多条近似平行的雨带和闪电高密度带只是华南和江南区域降水过程中的一个片段。分析结果表明:控制这片区域雨带活动的是南北两侧缓慢东移的扰动反气旋环流系统。在黄海扰动反气旋环流的南边缘和南海扰动反气旋环流的北边缘各形成了一条扰动风切变线与湿涡度扰动线对应,在它们之间形成了一个扰动低压气流区和其中的多个湿涡度扰动条带,决定了其中条状雨带的走向。分解欧洲中期天气预报中心(ECMWF)模式产品可以提前1~5天获得指示两个扰动反气旋环流系统和扰动低压气流区中湿涡度扰动分布的信息。

During the Dragon Boat rainy season(the time around the Dragon Boat Festival),there are usually some parallel bands in the precipitation area,and extreme rainstorm could cause disasters like flood and landslide.The current study decomposes atmospheric variables into temporal climatology and anomalous components and uses the latter to reveal the basic features of extreme rainfall during the Dragon Boat rainy season.The central and northern regions of Guangdong Province experienced an extreme rainstorm process accompanied by parallel rainfall bands and lightning high-density zones from 5 to 9 June 2020.This process happened in the relatively weak anomalous low over the central and southern parts of the country.Results showed two anomalous anticyclone systems,situated at the Yellow Sea and the northern South China Sea respectively,controlled the movement and location of the anomalous low.Meanwhile,the anomalous convergence lines and moist vorticity anomaly lines indicated the location of rainstorms in the anomalous low area.These features can be extracted from the product of ECMWF model 1~5 days in advance,to be useful to predict the rainfall storms during the Dragon Boat rainy season.