广东西部沿海一次致灾暴雨的中尺度分析

Mesoscale Analysis of a Disastrous Rainstorm Along the West Coast of Guangdong Province

2016年5月28日广东西部沿海发生了一次致灾暴雨过程,该文利用区域自动站、多普勒雷达等常规观测资料以及NCEP/NCAR再分析资料,分析此次降水过程的中尺度天气系统演变特征和维持机制。结果表明:①此次暴雨过程发生在季风槽西南急流中,西南急流为暴雨提供了不稳定能量,同时充足的水汽含量、显著的水汽辐合以及达到20×10^(-6) hPa·s^(-2)垂直螺旋度,都有利于强降水系统的生成、发展和维持。②分析中尺度对流系统(MCS)表明,MCS(b)和MCS(c)是造成此次降水的主要系统,两者同时生成后,迅速合并和加强,并维持在原地少动。分析雷达资料表明,此次强降水具有明显的后向传播性和列车效应,雷达回波性质是以积状云为主的混合性的降水回波,该类回波具有效率高,时间长等特征。③分析区域自动站地面资料特征表明,沿海中尺度辐合线上不断激发新对流云团和辐合线南北两侧较大的温差梯度,对强降水的发生发展提供了较好的抬升触发条件,同时江门和阳江沿海的“喇叭口”地形使得对流加强。

On May 28,2016,a disastrous rainstorm occurred along the western coast of Guangdong Province.Using the conventional observation data such as regional automatic station,Doppler radar and NCEP/NCAR reanalysis data,this paper analyzes the evolution characteristics and maintenance mechanism of mesoscale weather system of this precipitation process.The results show that:①the rainstorm occurred in the southwest jet of the monsoon trough,which provided unstable energy for the rainstorm.At the same time,sufficient water vapor content,significant water vapor convergence and vertical helicity of 20×10^(-6) hPa·s^(-2) are conducive to the formation,development and maintenance of the heavy rainfall system.②The analysis of mesoscale convective system(MCS)shows that MCS(b)and MCS(c)are the main systems causing the precipitation.After the two systems are formed at the same time,they merge and strengthen rapidly,and maintain at the same place with little movement.The analysis of radar data shows that the heavy rainfall has obvious backward propagation and train effect.The radar echo is a mixed precipitation echo mainly composed of cumulus clouds,which has the characteristics of high efficiency and long time.③The analysis of the surface data of regional automatic stations shows that the new convective cloud clusters and the large temperature gradient on the north and south sides of the convergence line are continuously stimulated along the coastal mesoscale convergence line,which provides a good lifting trigger condition for the occurrence and development of heavy rainfall.At the same time,the"trumpet mouth"topography along the coast of Jiangmen and Yangjiang strengthens the convection.