Analyses Of A Rainstorm Process In Jilin Province In2010

Northeast cold vortex is one of the major weather systems that impact Jilin Province, which often causes thundershowers in summer of Jilin Province, sometimes there is a regional storm or heavy rain. Therefore, analyses of typical case of heavy rain caused by the Northeast Cold Vortex could help us understand the northeast cold vortex weather and improve the level of forecasting storm. By this way, we could provide the forecasting service for the industry in time, reduce the loss of life and property, and achieve the purpose of disaster prevention and mitigation.Based on the synoptic diagnostic method, and using the routine observational data, the satellite cloud image data and NCEP reanalysis data, we analyzed the wide range heavy rainfall process in Jilin province, which occurred from July27to29,2010, including the large-scale circulation, mesoscale features, moisture sources and transport conditions, power conditions, unstable conditions and the characteristics of evolution and development of satellite images.Nine results as filows:(1) The wide range heavy rainfall process in Jilin province appeared in the mature stage of development of the northeast cold vortex during July27to29,2010. The establishment and development of the cold vortex situation at500hPa prodided a favorable large-scale circulation for the torrential rain. The stability of Okhotsk blocking high made the cold vortex move slowly, so warm and cold air intersected for very long time in Jilin Province;(2) The southward invasion of the strong cold air at850hPa, which was accompanied with a cold vortex, triggered the torrential rain;(3) The intersection and long stay of the warm and cold front in Jilin Province was the main reason for the torrential rain. The strong precipitation area moved along with the warm front on the ground;(4) The visible light cloud image with1.25km resolution could help us analyze the convective cells and many details of the characteristics of convective clouds. The features of overshooting top and dark shadow could help us identify the convective cell developing trend and direction of movement, and contributed to the monitoring and early warning of severe weather; (5) Dark areas of the vapor cloud image were associated with sinking motion, and it corresponded to the dry and cold air at upper altitude. The bright areas reflected distribution of water vapor at the upper level and the atmospheric movement of the middle troposphere. The rainstorm appeared in the region wheret left branch of the jet and the dry cold air on northern intersected;(6) Before rainfall water vapor came from the South China Sea and direction of moisture transport was mainly latitudinal in lower troposphere. During later time there was supplementary moisture from inland. Precipitation intensity altered as the value of moisture convergence changed, but the relation between them was nonlinear;(7) There was a significant increase of specific humidity before precipitation. We analyze the changes of the specific humidity to determine the start time of precipitation in the forecasting process. The maintaining time, during which the specific humidity below850hPa was larger than10g/kg, could be used to predict the duration of prediction;(8) There was a certain relationship between the distribution of positive vertical helicity center at850hPa and the strong convective clouds development and movement over Jilin Province. The area of heavy precipitation was located at positive vertical helicity center;(9) The emergence and reinforcement of negative moist potential vorticity(MPV) at850hPa, which may give a clue to the heavy precipitation. The area of heavy rain was in the positive and negative transition zone of the MPV, and was more close to positive zone.