The Mesoscale Convective Cloud Cluster Features of a Severe Torrential Rain Caused by Southwest Vortex

By using TBB data of FY2-C infrared images,radiosonde data and the rainfall data(including National weather observation stations and the region weather observation stations) at 1 hour intervals,the rare torrential rain weather event happened at south region of Sichuan Basin from 8th to 10th,July,2007 is compared.The results show that the extremely heavy rainstorm is caused by four mesoscale convective systems(two MCC and two MCS),which continual appearing and disappearing in the Southwest Vortex weather system.At its initial stage,there was a huge mesoscale convective complex(MCC) developed intensively along the basic air current direction.Because the rain region was quick along with the system migration,it had not led to the flood disaster,although the cloud cluster developed exuberantly in this stage.After this cloud cluster weakened,the Southwest Vortex circulation still maintained and kept little movements,and triggered three mesoscale convective systems(MCSs) one by one,which moved against basic air current slowly with the more obvious characteristic of low vortex.The later three MCS created rainfall region centralized,precipitation intensity strong,long-time maintained.all these results in the severe torrential rain.The heavy precipitation of forward development system are in front of its development and behind cold cloud center,The heaviest precipitation appeared when the cloud cluster development was fiercest,before being mature.The strong precipitation of the low vortex cloud cluster which backward development was mainly nearby cold cloud center,and the strongest precipitation appears when the cloud cluster was strongest(TBB of cloud center to be lowest).