Diagnostic Analysis of a Heavy Rainfall in Northeast Sichuan Basin Autumn

On the basis of the 24-hours precipitation data from the encrypted precipitation station,and NCEP reanalysis data,as well as Barnes band-pass filter,the mesoanalysis of a heavy rainfall happening in northeast Sichuan Basin on August 30 to September 1,2012 was analyzed.The results show that Under the environmental field of The cold air after Plateau trough and the southwest airflow of warm and moist on the northwest side of the subtropical high,the mesoscale depression was the directly influence system of this heavy rainfall.Low level southwest jet not only provided plentiful vapor for heavy rainfall in northeast Sichuan Basin,but also but also provided favorable dynamic condition and energy source for generation and development of the mesoscale system.Large scale environment field provided water vapor source and energy,and convection happened under stratification instability which made latent heat released as well as made a contribution to water vapor convergence and upward water vapor transfer.The configuration of low level convergence and high level divergence were beneficial to the genesis and maintenance of this heavy rainfall.