山东高唐EF3级龙卷S波段双偏振雷达探测特征

利用济南CINRAD/SA-D双偏振天气雷达的探测数据,结合龙卷实地调查资料,对2021年7月11日发生在山东聊城高唐的一次EF3级龙卷风暴的雷达回波演变过程、龙卷风暴单体的结构及龙卷风暴的中气旋(M)、龙卷涡旋特征(TVS)和龙卷碎片特征(TDS)进行分析。结果表明:(1)龙卷发生在高空冷涡及地面气旋共同作用天气形势下,龙卷位于地面气旋中心东偏北方向约200 km处;螺旋状对流云带中2个较强对流单体合并发展,演变成超级单体风暴,其后部下沉气流较强,与强的入流共同作用,诱发了强龙卷。(2)风暴中中气旋的顶高大多在5~7 km之间;龙卷发生前中气旋最大切变平均值为19×10^(-3)s^(-1),龙卷维持期间,中气旋最大切变平均值达到51×10^(-3)s^(-1)。(3)高唐龙卷涡旋底层双偏振参量主要特征是大的水平极化反射率因子,小的甚至负的差分反射率ZDR,小的相关系数CC;TDS时间及空间特征是,底层CC都小于0.7,CC低值区的面积在龙卷生成后随时间明显增大,CC值底层最小,随高度逐渐增大;CC低值区的面积低层和顶层较大,中间层较小;龙卷生成后TDS最大高度随时间逐渐增高,龙卷最强时TDS最高达到4.8 km,之后逐渐降低;龙卷消散后,1.5°以上TDS的特征很快消失,0.5°仰角TDS特征继续维持了大约11 min。

CINRAD/SA-D Dual Polarization Radar Detection Characteristic of EF3-Level Tornado in Gaotang, Shandong Province

Based on the detection data of CINRAD/SA-D dual polarization weather radar in Jinan and the field survey data of tornado, the evolution process of radar echo, the structure of tornado cell, mesocyclone (M), tornadic vortex signature (TVS) and tornadic debris signature (TDS) of a class EF3 tornado storm in Gaotang, Liaocheng, Shandong Province, on July 11, 2021, are analyzed. The results show that: (1) The tornado, which was located about 200 km northeast of the surface cyclone centre, occurred under the weather situation of the common effect of the upper cold vortex and the surface cyclone. The two strong convective cells in the spiral convective cloud zone merged and developed into a supercell storm. The downdraft behind the supercell was strong, which together with the strong inflow, induced a strong tornado. (2) The top heights of mesocyclones in storms were mostly between 5 and 7 km; the average maximum shear of mesocyclone before the tornado was 19×10^-3 s^-1; during the tornado maintenance period, the average maximum shear value of mesocyclone reached 51×10^-3 s^-1. (3) The main characteristics of the dual polarization parameters of the bottom layer of the Gaotang tornado vortex were large horizontal polarization reflectivity factor, small or even negative Z_DR and small C_C; the temporal and spatial characteristics of TDS were that the bottom C_C was less than 0.7, the area of the low C_C value area increased significantly with time after the tornado formation, and the bottom C_C value was the minimum, increased gradually with height; the area of the low-value area of C_C was larger in the lower and top layers, and smaller in the middle layer; the maximum height of TDS gradually increased with time after the tornado formation, and the maximum height of TDS reached 4.8 km when the tornado was strongest, and then decreased gradually; after the tornado dissipating, the TDS characteristics above 1.5° disappeared quickly, and the TDS characteristics at 0.5° elevation continued to maintain for about 11 minutes.