川渝盆地东部一次典型区域性暴雨特征及其西南涡发展机制

Study on the Development Mechanism of Southwest China Vortex in a Typical Regional Rainstorm in Eastern Sichuan Basin

利用多源观测、FY4卫星资料和ERA5再分析资料,对2022年6月26—27日川渝盆地东部一次西南涡暴雨天气过程的环流形势、中尺度对流系统发生发展以及卫星云图的演变特征进行诊断分析,并应用涡度方程探究造成此次暴雨过程的西南涡发展维持机制。结果表明:(1)此次西南涡暴雨天气过程是在多尺度天气系统有利配合下,冷锋裹挟近地面冷空气与低层偏南暖湿气流对峙交锋所导致的;(2)大尺度环流系统为西南涡的发展加深提供了动力条件,对流云团及强降水落区主要分布在低涡东侧及低层切变线附近的强动力抬升区,夜间西南气流的暖湿输送促使降水范围逐渐扩大且持续;(3)西南涡的发展维持主要受涡度平流项和水平散度项影响,其中地转分量使局地涡度不断减小,而非地转风分量则使局地涡度不断增加。

Based on multi-source observation data,FY4 satellite data and ERA5 reanalysis data,the evolution of circulation situation,the occurrence and development of mesoscale convective system and satellite cloud images of a Southwest China vortex rainstorm weather process in the east of Sichuan-Chongqing Basin from June 26 to 27,2022 were diagnosed and analyzed,and the development and maintenance mechanism of the Southwest China vortex that caused the rainstorm process were studied by using vorticity equation.The results show that:(1)This process was a Southwest China vortex rainstorm weather process formed by the cold front carrying cold air near the ground and the low-level southerly warm and humid air under the favorable cooperation of the multi-scale weather system.(2)The largescale circulation system provided dynamic uplift conditions for the development and deepening of the Southwest China vortex,and convective cloud clusters and strong precipitation areas were mainly distributed on the east side of the low vortex and near the low-level shear line in the strong dynamic uplift area.The warm and wet transport of the southwest airflow at night promoted the gradual expansion and continuation of precipitation range.(3)The development and maintenance of vortex were mainly affected by the advection term and horizontal divergence term of vorticity,in which the geostrophic component made the local vorticity continuously decrease,while the non-geostrophic wind component made the local vorticity continuously increase.