The Analysis of a Heavy Rain Process in July 2011

A heavy rain process occurred in central and eastern Sichuan province in early July 2011,diagnostic analyses are given by using NCEP reanalysis data,routine sonde and surface observation data,automatic weather station data and black body temperature data of FY-2E meteorological satellite.The analysis results show that,the mainly affect system of the regional heavy rain is southwest airflow around the subtropical high in West Pacific and mesoscale convective cloud cluster,the subtropical high extends westward meanwhile brings abundant warm and humid air flow to Sichuan,confluent with dry and cold air from north in Sichuan province,which enhances unstable atmospheric stratification;the rain areas have ascend motion and in low-level instability was hot and humid;700hPa moisture flux divergence analysis showed that the rainstorm water vapor is from the Bay of Bengal,and in the moisture convergence zone there is big value of TBB,apparent heat source and apparent moist sink;analysis of apparent heat source and apparent moist sink suggests that this process is a convective process,and condensation heating plays an important role in the atmospheric heating.Apparent heat source,apparent moist sink and vertical helicity have good correspondence between the rainstorm.When heavy precipitation occurs helicity is negative at higher levels and positive at lower levels;the water vapor budget over rain area shows that both north and south border are the main moisture sources,and the moisture supply is mainly from the convergence of north and south boundary.