Study And Application Of The Diversity Of Convection Development Under Different Synoptic Background Over Jianghuai Region

Convective weather in Jianghuai area has features of frequent occurrence,more types and strong catastrophability,and its extremes had the trend of aggrandizement in recent years.The strong convective weather has obvious regional characteristics.The researches about strong convective weather over Jianghuai area,especially about the convection types and development diversity under different synoptic background,lack systematic analysis.On the basis of analysis on climatic features and weather typing of strong convection,systematic analysis of atmospheric environment and storm features under different synoptic background,this paper focuses on the convective weather features,adopts multi-source observation and analysis data,uses numerical simulation,combined with the variety of strong convective weather development in Jianghuai area.The physical mechanism of development and convective storm features of strong convective weather with high catastrophability like hail,tornado and short-time heavy rainfall under cold eddy,edge of subtropical high plum rainfall and typhoon were analyzed further.Furthermore,the numerical simulation was used to emphatically analyze the sensibility of convective storm structure and intensity to environment.Finally,based on theoretical study,the research about potentiality of strong convective weather with environment of convective parameters and categorical forecast method was carried out.Conclusions are as follows:1.Through the climatic analysis of different types of strong convective weather in Jianghuai area,the variety features of strong convective weather was analyzed systematically and completely,five typical weather:before trough,after cold eddy,subtropical high borderline,subtropical high control and tropical system,causing convective weather were concluded and refined,and the occurrence regions and frequency of different types of convective weather under different synoptic background was studied.2.The difference of occurrence region and frequency in conclusion one and convective storm structure of different convective weather result from the weather system configuration and environment conditions of atmospheric temperature,humidity and dynamic under different synoptic background,which were all revealed.3.Through case analysis,the similarity and difference of triggering,development mechanism of strong convective weather with high catastrophability like hail,tornado and short-time heavy rainfall under cold eddy,edge of subtropical high plum rainfall and typhoon were analyzed.(1)The effects of cold advection guided by the northerly wind disturbance at the back of middle-high level cold eddy of under cold eddy on the unstable stratification construction,the triggering and mutual feedback mechanism of ground convergence system(convergence line or mesoscale cyclone)to strong convective weather and the difference of dynamic environment in the convection system development process in different seasons were all revealed.(2)The research on tornado in meiyu period over Jianghuai area found that its formation condition under mesoscale eddy environment,unstable stratification,lower vertical wind shear,water vapor,unstable energy,as well as the supercell storm structure characteristics shows a considerable aspect of consistency,at the same time,the part of the environment conditions and structure features also show the common features different from other strong convective weather.(3)The difference of convection development in typhoon causing rainfall periods at different stages was analyzed.The cold air participation is crucial.Cold air invasion on one hand can promote the development of convective unstable stratification,on the other hand,the intersection with the convergence up warm moist air in typhoon low pressure inverted trough can cause the middle frontogenesis,and through the low-level wind field disturbance,the local convergence and cyclonic vorticity were strengthened,the medium and small scale convective systems were triggered,which caused the local rainfall and rapid development of convection.4.The sensitivity test was used to reveal the higher sensitivity of convective storm development and its structure to changes of environment,wind and water vapor.The variation of water vapor in the lower troposphere had obvious effects on convection strength and development speed at the initial stage.The strengthening environmental wind in the middle-low layer would pronmote the development of convection.The increasing middle layer wind field was beneficial to the enhancement of convective storm rotation in middle level,the decreasing of storm scale and the stronger convection development.Low-level wind field development was beneficial to the development of the storm secondary circulation in lower layer and cyclonic vorticity in middle-lower layer on inflow side.5.On the basis of the difference features of physical mechanism and forming environment of the different types of strong convective weather,the relevant theories like fuzzy mathematics,grey system and economics were introduced,the relative deviation fuzzy matrix evaluation technology of multi-obj ective decision-making,probability matching technology,day by day slipping technology,etc.,were used to effectively solve the weight allocation problem in the process of convective parameters selection,to eliminate the climatic difference between the regional and seasonal convective parameters,moreover,combined with the mesoscale numerical model,the strong convective weather potentiality and categorical forecast system was established.