“6·23”江苏阜宁EF4级龙卷超级单体风暴中尺度结构研究

2016年6月23日14—15时，江苏省阜宁县突遭"增强藤田"4级龙卷、强风、短时强降水和冰雹等强对流天气，致使99人罹难，800多人受伤，属极其罕见的极端天气事件.本文利用加密自动站数据、探空数据、单部雷达观测数据以及双多普勒雷达三维风场反演数据，研究了此次龙卷发生的天气背景、龙卷超级单体的三维结构及其演变特征.研究表明：（1）龙卷发生期间，阜宁处于地面暖湿舌内、地面有γ中尺度气旋和辐合线；环境大气抬升凝结高度很低、中低层有很强的水平风的垂直切变；这有利于龙卷的生成.（2）此次龙卷超级单体左移风暴的低层有钩状回波和入流缺口，有界弱回波区位于垂直剖面中低层、悬垂回波位于风暴前部高层.（3）龙卷发生前，风暴质心高度、最大反射率因子高度和风暴回波顶高度均持续增加，风暴垂直累积液态含水量激增；龙卷发生在上述参数的数值首次同时减小时.（4）双多普勒雷达反演的三维风场揭示，超级单体形成之前的对流风暴内部中低层已经有中尺度气旋形成，中尺度气旋伴随着超级单体的生成、发展和强化的各个阶段.中尺度气旋位于钩状回波顶端、其南端有反气旋，此涡旋偶对于中层动量下传、龙卷生成、发展、加强和触地具有重要作用.

Observations of 23 June 2016 EF4 tornado supercell thunderstorm mesoscale structure in Funing county,Jiangsu province

The enhanced Fujita 4 scale Funing county tornado outbroken on 23 June 2016, was the most significant tornado in Jiangsu province since 1961. The tornado fatalities and injuries were 99 and more than 800, respectively. This paper addressed the synoptic environment, the thermodynamic condition, and the three-dimensional fine scale structure of the tornadic supercell thunderstorm. The data sources include the automatic weather station,radiosonde, and Doppler weather radar. This supercell thunderstorm developed under a convectively unstable environmental condition. The lifting condensation level was at 987.5 hPa, and the environmental wind vertical shear was intense at the low and middle level. Convergence lines and a γ-mesoscale cyclone were observed on the surface.The thunderstorm was a typical left-moving supercell with a prominent hook echo and an inflow notch at the low level.The bounded weak echo region was at the middle level, and the intense storm top divergence was at the upper level.A severe mesocyclone was observed by Doppler radar at the low and middle level. It was located in the top of the hook echo, lasted for more than 1.5 hours. The tornado vortex signature lasted for 12 volume scans, which was 46 minutes before the tornado occurrence. In the period of tornado formation and intensification, the storm top, the center of the storm mass, and the height of the maximum reflectivity rose. The vertical integrated liquid of the storm increased remarkably, too. The tornado occurrence was in the first time of the above-mentioned parameters decreased synchronously. The retrieved wind fields from Huaian and Yancheng dual-Doppler radar data showed a mesocyclone at the low level of the convective storm. After the convective storm developed to a supercell thundstorm,the mesocyclone was located at the low and middle level of the hook echo high-reflectivity region. At the same time, a weaker anticyclonic circulation was shown on the south of mesocyclone. The vertical vorticity couplets straddled the high-reflectivity region of the hook echo. It played an important role on the tornado formation, intensification, and maintenance.