一次超级单体引发的秋季特大冰雹和龙卷雷达探测分析

Radar Observation Analysis of Severe Hailstorm and Tornado Caused by a Supercell in Autumn

利用烟台S波段双偏振多普勒雷达和荣成CINRAD/SA新一代天气雷达探测数据,结合探空、地面气象观测、ERA5再分析和冰雹、龙卷实地调查等资料,对2021年10月1日在山东半岛东部烟台、威海发生的特大冰雹和龙卷风暴的天气形势、环境参量和雷达探测特征进行分析。主要结果为:与气候平均场相比,造成本次强对流过程的500 hPa东北冷涡异常强盛,850 hPa自华南到东北地区西部有持续偏南水汽输送;在此异常环流背景下,山东半岛东部具有上干冷下暖湿、强的0~6 km垂直风切变和对流有效位能等有利于强冰雹、龙卷发生的环境条件;近地面的风暴前低压、雷暴高压和冷池特征明显。降雹时的风暴呈现典型超级单体特征,低层具有明显的钩状回波和倒“V”字型前侧入流缺口,垂直剖面显示出明显的有界弱回波区、差分反射率柱(Z DR柱)特征;根据大冰雹落点和降雹开始时间等信息,统计对应雹云的反射率因子、Z DR、相关系数(CC)的中位数分别为48.7 dBz、0.89 dB和0.90;地面出现龙卷和大冰雹时,风暴顶辐散强度最大达到71.5 m·s^(-1)。后侧阵风锋对应的出流边界北端的偏北气流与风暴前侧的偏南气流形成强涡旋上升运动,导致EF1级龙卷产生;龙卷发生在钩状回波的顶端,大冰雹多出现在入流缺口的北侧。地面发现龙卷发生前约5 min,雷达探测到龙卷碎片特征,Z DR和CC分别最低至-0.1 dB和0.81;龙卷发生前约11 min,探测到风暴低层的Z DR弧和风暴右后侧的下沉反射率因子核特征;荣成、烟台雷达分别提前22 min、5 min识别出中气旋和龙卷涡旋,可为龙卷预警提供重要参考。基于观测分析,给出了本次超级单体风暴的低层流场及龙卷、大冰雹落区的示意图。

Using observation data from Yantai S-band dual polarization Doppler weather radar,Rongcheng CINRAD/SA radar,radiosonde and surface meteorological stations,as well as the ERA5(ECMWF reanalysis data)and the hail,and tornado information obtained from field surveys,this article analyzes a severe hailstorm and tornado that occurred on 1 October 2021 in the eastern part of Shandong Peninsula.The results are as follows.Compared to the climatic mean field,the 500 hPa northeast cold vortex responsible for this severe convective process was extremely strong,and at 850 hPa there was continuous southward water vapor transport from South China to the west of Northeast China.Under the abnormal circulation background,the atmospheric thermal and dynamic conditions,such as dry and cold in the upper troposphere,but wet and warm in the low troposphere,with strong 0-6 km vertical wind shear and convective available potential energy(CAPE)on the eastern Shandong Peninsula,were very favorable for the occurrence of severe hailstorm and tornadoes.The features of pre-storm low pressure,thunderstorm high pressure,and cold pool were obvious near the surface.During the hail period,the supercell features were very typical,with distinct hook-shaped echo and inverted“V”anterior inflow gaps in the lower layers,and vertical profiles showed distinct bounded weak echo region(BWER)and differential reflectivity(Z DR)column characteristics.According to the large hail location and starttime information,the median values of reflectivity factor(Z H),Z DR and correlation coefficient(CC)were 48.7 dBz,0.89 dB and 0.90 respectively.When tornado and severe hail appeared on the ground,the maximum storm-top divergent outflow reached 71.5 m·s^(-1).The cold pool airflow at the northern end of the rear flank gust front(RFGF)and the south inflow on the pre-storm side formed a strong vortex upward motion,resulting in an EF1-level tornado.The tornado occurred at the top of the hook-like echo,and large hailstones appeared on the north side of the inflow gap.About 5 min before the tornado,the radar detected the tornadic debris signature(TDS)features,with Z DR being as low as-0.1 dB and CC as low as 0.81.About 11 min before the tornado genesis,the Z DR arc in the lower layer and the descending reflectivity core(DRC)in the rear flank side of the supercell was detected.Rongcheng and Yantai radars identified mesoscale cyclones and tornadic vortex signature(TVS)about 22 min and 5 min in advance,respectively.This can provide an important reference for tornado warning.Based on the observation analysis,the schematic diagram of the low-layer air flow field and the tornado and large hail-falling area of the supercell storm is summarized.