一次东北冷涡暴雨过程中尺度及云物理特征分析

Mesoscale and Cloud Physical Characteristics Analysis of a Northeast Cold Vortex Rainstorm

利用WRF数值模式对2019年7月16日发生在东北冷涡底部的暴雨过程进行数值模拟,使用常规观测资料、卫星云图和数值模拟结果对此次暴雨过程的中尺度及云物理特征进行分析。结果表明:东西2个暴雨区分别由MCC和MCS活动造成的。MCC发展的环境具有低层更暖湿、高层干冷,对流不稳定更强,垂直风切变更大的特点,有利于酝酿更强的风暴。降水回波与地面辐合线同时出现,共同移动,两者有正反馈作用。与西部回波相对应的辐合线辐合更强,北侧偏北风风速更大,移动更快,对应的强降水范围更小、降水时段更集中。而东部暴雨区相对应的辐合线两侧风速均较小,呈准静止态,回波长时间在辐合线附近维持,列车效应形成暴雨,对应的强降水范围较大、持续时间更长。降水过程中霰和雪是对流云中主要的降水粒子,通过冷云增长;雨水的增长主要依赖于霰和雪的融化,其次还有暖云中云水的碰并增长。

Based on the conventional observation data,satellite cloud images and numerical simulation by WRF,the mesoscale and cloud physical characteristics of the rainstorm occured at the bottom of a northeast cold vortex on July 16 th 2019 is analyzed.It shows that,the eastern and western rainstorm areas are caused by MCC and MCS activities respectively. The development environment of MCC was characterized with warm wet in the lower layer and dry cold in the upper layer,as well as strong convection instability and large vertical wind shear,which were more favorable for the occurrence of stronger storms. Precipitation echo and ground convergence line appeared at the same time,moved together with a positive feedback effect to each other. The convergence line corresponding to the western echo had higher wind speed,faster movement,stronger convergence,smaller range of heavy precipitation and more concentrated time. On both sides of the convergence line corresponding to the eastern rainstorm area,the wind speed was relatively small,showing a quasi-static state. The echo maintained near the convergences line with a long duration,and the train effect induced the rainstorm with larger coverger and longer duration. Graupel and snow were the main precipitation particles in convective clouds and growed through cold clouds in the precipitation process. The growth of rain water content mainly depended on the melting of graupel and snow,followed by the collision and growth of cloud water in warm clouds.