一次西南涡引发MCC暴雨的卫星云图和多普勒雷达特征分析

Analyses on Satellite Cloud Images and Doppler Radar Echo Features of a MCC Rainstorm Caused by Southwest Vortex

利用常规观测资料、自动站资料、卫星资料和多普勒雷达资料,对2008年6月30日至7月1日发生在滇东北和四川盆地南部一次暴雨天气过程的分析发现,850 hPa四川盆地南部西南涡引发的中尺度对流复合体(mesoscale convective complex,MCC)是暴雨的直接影响系统,700 hPa青藏高原东南侧西南涡引发的中尺度对流云团并入MCC后导致MCC迅速加强并向西移动。MCC生成于对流层高层急流出口区左侧强辐散区和低层强辐合区。雷达回波上"人"字形回波、平行短带回波和逆风区的出现说明MCC内部存在多个β中尺度对流系统,直接造成多个暴雨中心。MCC成熟阶段表现出中低层辐合和高层辐散的动力特征,其前沿中层以下有强气流流入,以上则有强气流流出。MCC消散阶段从低层到高层都有强西南气流进入,相应气流辐合减弱,失去中尺度组织结构。

A rainstorm occurred in the northeast of Yunnan Province and the south of Sichuan Basin from June 30 to July 1,2008 is analyzed based on routine observation data, automatic station data, satellite cloud images and Doppler weather radar data. The results show that the mesoscale convective complex（MCC） caused by the southwest vortex at 850 hPa in the south of Sichuan Basin is a system directly influencing the rainstorm. MCC is rapidly strengthened and moves westward after the combining with the mesoscale convective cloud cluster caused by the southwest vortex at 700 hPa in the southeast of Ti- betan Plateau. MCC appears in the divergent region on the left of jet exit at high level and the convergent region at low level. The emergence of special structure echo like ＂人＂ character, parallel short belts echo and mid-altitude radial convergence （MARC） in radar echo picture indicate that there are several fl mesoscale convective systems in MCC, which directly cause the several heavy rainfall centers. In maturity stage of MCC, Radar echoes demonstrate the dynamic characteristics of low-level convergence and high-level divergence, with strong inflow below middle level and strong outflow above middle level. In dissipated stage of MCC, there is strong southwest inflow from low level to top level, in such a way that the convergence is weakened and the mesoscale structure disappears.