Analysis of a Large-scale Severe Precipitation Event in Jilin Province From 27 to 29 July 2010

By using the routine observational data,the satellite images and NCEP reanalysis data,preliminary analysis on a large-scale severe precipitation event in Jilin province from 27 to 29 July of 2010 was made based on synoptic diagnosis.The main results are as follows.1) The formation and continuance of cold vortex circulation in 500 hPa provided the advantageous large-scale circulation background for the origination and development of torrential rain,and the southward invading of strong cold air with the cold vortex in 850 hPa triggered the torrential rain.2) The continuance of surface cold front and surface warm front resulted in a long-time confluence of cold air and warm air over Jilin,which was one of cause for emergence of torrential rain.3) Large quantities of instable energy and water vapor were conveyed by low level jet in 850 hPa to the torrential rain region providing sufficient energy and moisture conditions for the formation of rain.Meanwhile the moisture from the Yellow Sea and the East China Sea was continually conveyed by the extreme low-level south jet of more than 12 m·s-1 in 925 hPa to the torrential rain region playing an important role in the development of the torrential rain.4) Water vapor was from the South China Sea in the prophase of rainfall,and its transport was mainly northwards in lower troposphere,while there was supplementary moisture from inland in the later of rainfall,and the distribution of rain was better corresponding with the water vapor convergence in lower troposphere,but there was not a whole linear relationship between them.5) There were the formation,development and dissipation of four main meso-scale convective clusters in the whole process,and the mature stage of each meso-scale convective cluster corresponded to the precipitation period,and the region of each meso-scale convective cluster matched the region of rainfall.