Study On The Occurrence Characteristics And Typical Weather Cases Of Local Rainstorm In Liaoning Province Under The Background Of Northeast Cold Vortex

Since 1979,the local rainstorm caused by the CVNE is frequent,accounting for79% of the total rainstorm days caused by the CVNE.Based on NCEP / NCAR 1 °×1 ° reanalysis grid data,precipitation data of 62 national meteorological stations in Liaoning Province,hourly encrypted precipitation data and rainstorm disaster data from 1979 to 2019,this paper analyzes the distribution characteristics and change rules of the local rainstorm in the CVNE,and discusses the occurrence rules of local rainstorm in different types and in different periods of it combined with rainstorm frequency and precipitation in order to deepen the understanding of the local rainstorm occurrence and development mechanism of CVNE.To improve the ability of prediction and analysis,and further provide reference for improving the accuracy of local rainstorm prediction under the background of CVNE.The specific research results are as follows:(1)Among the local and non-local rainstorms in Liaoning caused by CVNE in Northeast China,the proportion of local rainstorm days is more than others,reaching95% in June.This type of rainstorm occurred in early April,with a multiple increase in June and a peak in July,occurring earlier than non-local rainstorms,with a period longer than non-local rainstorms.The interannual variation is decreasing year by year and is more likely to occur in coastal areas.(2)The average life of the CVNE process causing local rainstorm is 4.5 days,with a maximum of 13 days,with 4-7 days accounting for 48%.The center of vortex is between 45-55°N or 115-130°N E,which is the most prone to local rainstorm.The number of local rainstorm days in the weakening period was 103,accounting for48%.The second is development period,the least is maturity period.The total rainfall during the development period is large,and the rainstorm in the weak period is more localized.(3)Through the comparative analysis of local rainstorm in CVNE,it is concluded that the water vapor condition in the developing period is best.In the development stage,the specific humidity of the whole layer is generally good and stable,while in the mature stage,the specific humidity decreases,while in theweakening stage,the specific humidity is unstable and fluctuates greatly.The thermal condition is the best in the weakening period and the worst in the mature period.During the development period,the cold and warm center was the strongest and appeared in pairs,the dry and cold air invaded over the local rainstorm,and the cold and warm center weakened in other periods.The dynamic conditions are most unfavorable in the weakening period.During the development period,the positive and negative centers of the vertical velocity over the rainstorm area are easy to form a pair,and the low-level jet stream increases from the development to the maturity period.(4)According to the three typical local rainstorm process,mature and weakening CVNE systems,The specific humidity of the atmosphere below 850 h Pa increases and decreases rapidly before and after the rainstorm,and the maximum value can reach 9-12g/kg.The effective convective potential energy(CAPE)and pseudo equivalent potential temperature(?se)are located in the region with large CAPE??se gradient during development and weakening.the physical quantity of wet vortex is suitable for local rainstorms caused by CVNE,MPV1 is negative and MPV2 is positive in the lower atmosphere.