Characteristic Analysis of Cloud Images and Radar Data on a Mesoscale Rainstorm Cluster in the West of South China

A large scale rainstorm hit the West of South China on 19-20 June 2010, with its rainfall center in Yongle County, Liuzhou City, and rainfall of 221.4mm in 24hr. Comprehensive analysis was conducted for this rainstorm process, by using data of conventional measurement, rainfall, TBB from FY2 and Doppler radar. It shows that:(1)Mesoscale Convective Complexes(MCC) and the southwest jet in the low layer were the directive dynamics that induced the happening and developing of the rainstorm cluster.(2)Vertical shear(u200-u850) over the rainstorm region was small, under which circumstance the relative motion between the up and the down air was small, favoring the accumulation of thermal and moisture, and making the disturbance develop rapidly and form the rainstorm cluster. (3)The rainstorm cluster has the MCC features, with the cloud area of TBB≤-52°æ region growing rapidly in its developing state, and the cloud TBB soaring to be -82°æ or above in its mature state.(4) Doppler radar data showed that there were many developing convective clusters of ¦Ã-scale in the initial state of MCC, then they grew up to be 2 clusters of b-scale with 2 echo bands of 60 DBZ in the developing state, after that they merged and formed the integrative MCC, with the enhancement of rain intensity.(5) In the 0.50 radius field, there was a corresponding region of adverse wind in the¦Ã-scale convective cluster, where the region of positive velocity involved in the region of minus velocity. There was a strong convergence in the region of adverse wind, which would be benefical to the forming of MCC, inducing the happening of heavy rain.