| In this paper,the environmental field of the Jiangsu tornado events in the past 2009-2016 years was counted and diagnosed,and the environmental field of the two typical tornado process was numerically simulated to discuss the particularity of Jiangsu in the spring and summer seasons in the near coastal plain area as the most high frequency area of China's strong tornado,focusing on the characteristics of the complex tormado environmental field formed by the environmental mesoscale system and its superposition in the Jiangsu area.From the perspective of system superposition,uplift,rotation and stability,we analyze the environmental field of tornado strong convective weather.We hope that this study can provide important references for the theoretical research,simulation research and tormado prediction and early warning of tormado development in coastal plain area.According to the statistical analysis of the strong convective weather in Jiangsu province in the annual report of tlhe climate center of Jiangsu province in 2009-2016 years,it shows that the North Jiangsu area is the high incidence area of the tornado events in Jiangsu Province,and Yancheng and Xuzlou are the most prone areas of the tornado weather in Northern Jiangsu Province,the main occurrence period is the spring and summer season.The diagnosis and analysis of two strong convective environment fields in Peixian,Xuzhou(2009)and Funing(2016)in Yancheng show that the key systems of the two tornado strong convective convection are two mesoscale fronts,and the Xuzhou tornado environmental field is the front-end and the sea wind front,and the Yancheng tornado environmental field is a frontal cyclone and a shore front.In the environmental field,the inland system and the coastal zone system gradually converge and overlap,and the vertical sections near the front show that there is a strong two level circulation and vertical motion center in the middle and low layers,and the low level wind field has a strong rotation effect.The control experiments of two front superposition in flat area also showed that the high value area and relative helicity(SRH)of unstable CAPE were gradually expanded,gradually covered and increased gradually to Funing.And gradually get a strong center in the vicinity of Funing.In the high range of SRH,there is a SRH intensity center that presents the bulk of discrete clusters,showing that the superposition of the two fronts is conducive to the activity of the local small scale rotation system that is dispersed in the region.By increasing the sensitivity test of mountain terrain to change the terrain of Jiangsu Province,the effect of terrain on regional instability in the non plain area and the difference with the superposition of the plain two front system are discussed.The results show that,due to the proximity of the mountain and the cyclone front,and the north end of the coastal front shore front,the impact on the inland front system is stronger than the shore front of the coastal zone.The terrain sensitivity test also showed that the high value zone of CAPE(convective effective potential)and the high value area of SRH(relative spiral degree of storm)in the experiment were in the South and southeast of the mountains,and the range and intensity were basically stable,but the CAPE value was higher than that without the mountain control experiment,while the SRH value was less than half of the control experiment.It shows the instability caused by the constant blocking and lifting effect of the mountain range on the air flow,and the uplift strength of the terrain is greater than that of the system lift,and the constant rotation caused by the mountains is obviously less than the effect of the relative helicity SRH superimposed on the control experimental front system. |
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