Diagnosis of a Heavy Rain Process in Chongqing

Based on radar data,hourly rainfall data,TBB and NCEP reanalysis data,a heavy rain process on July 26,2011 in northeast Chongqing was analyzed in this paper.The results are as follows:(1)The low-level shear line triggered the formation and development of mesoscale convective system,and low level shear line had a good corresponding relation with the occurrence of the MCS,when vertical wind shear got to maximum,the convergence and the vertical ascending motion in the heavy rainfall area also got to maximum;(2)The lower water vapor from the South China Sea transported along the southwest side of west Pacific subtropical high,which convergenced and moved upward in the northeast Chongqing and provided sufficient water vapor for heavy rain;(3)TBB data analysis showed that two mesoscale convective clouds existed over Chongqing when strong rainfall occured,one of theγ-mesoscale convective system developed intoβ-mesoscale system,and the other one split during moving process;(4)The radar data analysis showed that upwind area appeared during heavy rainfall process,which indicated that the vertical circulation was stronger and it was useful for low level water vapor transportation upward.At the same time,the mesoscyclone generation was also helpful for warm wet air continuous transportation,and promoted the development of the heavy rain.