2019年辽宁开原龙卷风观测事实分析

利用加密自动站、FY-4A卫星及多普勒雷达等观测资料,对2019年7月3日辽宁开原突发龙卷天气进行分析.结果表明:在冷涡减弱阶段,中纬度冷空气活动频繁,冷涡底部500 hPa与850 hPa的短波槽垂直分布,利于辽宁北部对流不稳定加强.FY-4A可见光云图显示,开原龙卷生消迅速,有明显的上冲云顶.雷达反射率因子特征是,...

Observational Analysis of Tornado in Kaiyuan of 2019

Using the observation data of automatic stations,the FY-4A satellite data and the Doppler radar data,the sudden strong convective weather are analyzed in northern Liaoning on July 3th,2019.Results show that in the context of the weakening stage of the cold vortex,the cold air activity at mid-latitudes is frequent,and the short wave troughs at the bottom of the cold vortex on the 500hPa and the 850hPa levels form a forward-inclined structure,which is conducive to the strengthening of the convection instability in northern Liaoning.The tornado in Kaiyuan generates and disappears rapidly,and clear overshooting cloud tops on the visible images of the FY-4A satellite.The radar reflectivity factor is characterized by the combination of convective cells to a supercell,the continuous mesocyclone,the hook echo,and the three-dimensional display of a hollow structure;When the strong echo area is inclined to the side of the moving direction,there is a dome structure and a bounded weak echo area in the vertical section,and the tornado is most likely to occur in the hook echo area;The location of the cavity coincides with the central region of the mesocyclone and the hook-shaped echo,indicating that the supercell has a strong vortex there,which is conducive to the movement of the funnel cloud from the parent body to the ground.There are symmetrical positive and negative speed zones on the radar speed product.The rotation speed continues to increase,and the speed zones develop downward continuously.When the adjacent speed pair is detected at a low elevation angle,the mesocyclone also extends downward and shrinks rapidly,indicating the occurrence of tornado.The cold vortex in the northeast of China,the low-pressure zone in front of the Mongolian cyclone,and the invasion of cold and dry air on low levels caused the frontogenesis and other dynamic conditions,which are the triggering mechanism of the convection from Jilin to northern Liaoning on the weather and the middleαscale.Whereas the local heating near Kaiyuan generates updrafts,and the decrease of the surface pressure enhances the cyclonic convergence of the wind field and the development of the ascending movement,which are the triggering mechanism.