Mesoscale analysis of a rainstorm in Liaoning on July 31,2008

A heavy rainstorm in Liaoning on July 31,2008 was analyzed with 6-hourly FNL data of l°×l°, sounding data,surface observations,satellite images,associated filtering method and physical diagnosis,and the main results are:a synoptic analysis indicated that the cold trough at 500 hPa moved southward slowly and the western Pacific subtropical high jumped northward.Mesoscale systems forming in the warm sector of fronts directly contributed to the development of rainstorm and they could be well separated from the background field by the filtering method.There were two processes during the rainstorm:the first occurred in the warm sector rather than on the front surface and the rain belt in the second process moved northeastward.In the development period of the rainstorm,the large-scale and mesoscale systems facilitated the water vapor transport while they both reduced the supply of water vapor during the dispersion period of the rainstorm,suggesting that the mesoscale system plays an important role in the supply of water vapor during the development of a rainstorm.