Characteristics And Early Warning Of Tornado Storm Doppler Radar Products In Northern Jiangsu

Tornado is one of the important weather disasters in our country.As the high-risk zone of tornadoes in China,the northern Jiangsu area is often attacked by tornadoes,which poses a great threat to the safety of people's lives and property.value.In this paper,based on Doppler radar-based data,ERA-Interim and NCEP/NCAR reanalysis data,the spatial and temporal distribution characteristics of the tornado in northern Jiangsu are analyzed;the circulation pattern when the tornado occurs in northern Jiangsu is summarized.,And conducted a comprehensive analysis of the environmental conditions;finally,the Doppler radar product characteristics and early warning were explored.The results show:(1)From 2009 to 2018,the frequency of Jiangsu tornadoes increased first,then decreased,and then increased slightly.The tornadoes in Jiangsu mainly occurred in spring and summer,and the five northern Jiangsu cities were the most frequent occurrences of Jiangsu tornadoes.In the region,there were 48 tornado storms in northern Jiangsu,among which Yancheng had the most.(2)Summarize the three main types of weather patterns corresponding to the occurrence of the northern Jiangsu tornado:the cold vortex trough type,the subtropical high margin type and the tropical typhoon type.(3)Through the synthetic analysis of the environmental conditions of the northern Jiangsu tornado,the CAPE value in the northern Jiangsu area is in the range of800-1800J/kg.There is a high-value central area in Yancheng.The convection in this area is not effective effectively.The north region generally has a higher effective convection value than that of southern Jiangsu,but the CAPE at the time of the tornado is not very strong,and there are no significant characteristics of CAPE.The North Jiangsu area is in the negative SLI area,with an absolute value between 2-4,and the central large-value area is roughly consistent with the distribution position where convection fails effectively.In the lower troposphere,on the west side of the subtropical high,there is a pseudo-equivalent temperature zone with a northeast-southwest trend,and the?_sein the northern Jiangsu area is generally above 350K.The 925h Pa vorticity field in the northern Jiangsu area is positive,and the divergence field is mostly negative.It can be seen that there is significant convergence between the lower layer and the near ground surface,and the strength of the ascending airflow leads to the decompression of the ground and the strengthening of the cyclone,which is prone to strong convection the weather.The combination of the deep positive vorticity area and the ascending motion area provides good dynamic conditions for the production of the northern Jiangsu tornado.(4)Whether the tornado occurs in the northern Jiangsu area,whether it is a super-single tornado or a typhoon-type tornado,the main key echo characteristics should be placed on the hook echo,and the echo intensity exceeds 50d BZ;the radial direction before the tornado occurs The velocity field often exhibits cyclonic convergence,and the rising motion generated by the convergence can stretch the middle cyclone to a certain extent,which further strengthens the vortex motion,which in turn makes the tornado occur;the velocity spectrum is wide,and the vertical accumulation of liquid water Sudden changes,sudden drop in the height of the strong echo center,and the lowest value of the top and bottom of the storm for a period of time.Changes in these indicators indicate that a tornado is about to occur,and all have certain reference significance for early warning of the tornado.(5)The tornado weather process in Qundong Town,Dongtai City,July 29,2008was a non-super single tornado.The tornado occurred at the end of the bow echo caused by the squall line.After the bow echo of the squall line TVS was not detected due to the strong currents that were converging and the downwind caused by the anticyclone field;the East Taiwan Tornado on July 8,2017 and the Yan'an Hailstorm on June 12,2016These two strong convective weather processes showed typical characteristics of supercell storms.However,in terms of echo patterns,there was a three-body scattering phenomenon in the Yanan Ansai hail of 6.12 in 2016,and no three-body scattering occurred in the East Taiwan tornado process spike.The VIL value during the hailstorm in Yan'an,An'an was significantly higher than the VIL value during the Dongtai tornado.This indicates that the water vapor content in the cloud is very high,which is also the reason why there is no hail weather accompanying the Dongtai tornado.The Yanan hail process belongs to a typical high-mass convection system,but the occurrence of tornado storms is more inclined to the low-mass convection system.Therefore,although the Yanan hail process has a strong vertical wind shear and unstable stratification in the lower layer,it is because of the supercell The storm's new system of high center of mass cannot lead to the tornado process.