袁潮,李得勤. 2022. 冷涡背景下一次微型超级单体龙卷的雷达特征和物理过程探究[J]. 气象学报, (0):-, doi:[doi]
冷涡背景下一次微型超级单体龙卷的雷达特征和物理过程探究
A Case Study on the Radar Characteristics and Physical Process Involved in the Genesis of a mini supercell Tornado under the background of cold vortex
投稿时间:2022-03-21  修订日期:2022-06-13
DOI:
中文关键词:  龙卷  双偏振雷达  微尺度气旋  地面辐合线  龙卷形成
英文关键词:Tornado, Dual polarization radar, Misocyclone, Boundary, Tornadogenesis
基金项目:国家重点研发计划项目(2018YFC1507305);环渤海科技协同创新项目(QYXM202101);气象预报业务关键技术发展专项(YBGJXM(2019)01-05);中国气象局预报员专项(CMAYBY2020-026)
作者单位邮编
袁潮 中国气象局沈阳大气环境研究所 110166
李得勤 中国气象局沈阳大气环境研究所 110166
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中文摘要:
      2019年8月16日渤海湾北部沿岸出现了一次冷涡背景下的EF1级龙卷。利用营口S波段双偏振多普勒天气雷达观测资料、5min间隔的地面自动气象站观测资料、盘锦风廓线雷达资料及ERA5再分析资料,研究了该龙卷风暴产生的环境条件、龙卷风暴结构特征及龙卷形成的可能物理过程。结果表明:此次龙卷过程发生在500 hPa冷涡主体控制下,低空位于“利奇马”台风残涡西侧水汽输送带内,环境条件表现为弱的垂直风切变和强低层热力不稳定。营口双偏振雷达位于龙卷发生地15 km处,探测到产生龙卷的微超级单体钩状回波、下降的反射率核心(DRC)、弱回波洞(WEH)、龙卷残片特征(TDS)等结构。旧雷暴阵风锋出流向西传播,而营口附近海风锋缓慢东移,两条边界层辐合线相遇加强,在水平切变不稳定的作用下,辐合线上有γ中尺度涡旋形成。辐合线相遇造成的辐合抬升,低层强热力不稳定导致的环境正浮力以及中层中气旋扰动低压共同作用产生强烈上升气流,γ中尺度涡旋与上升气流叠置,强拉伸作用增强了垂直涡度,可能为形成低层微尺度气旋(misocyclone)的关键机制。misocyclone的最大旋转速度与最小直径相耦合对应龙卷生成,中层中气旋与misocyclone相互扯离对应龙卷消亡。
英文摘要:
      An EF1 tornado occurred on the northern coast of the Bohai Bay under the background of cold vortex on 16 August 2019. Using the Yingkou S-band dual-polarization Doppler weather radar data, surface Automatic Weather Station(AWS) observations at 5-min interval, the Panjin wind profile radar data and ERA5 reanalysis data, the environmental background , the structure and formation of tornadic storm and the tornadogenesis were studied. The results show that the tornado occurred under background of 500 hPa-cold vortex, and located in the water vapor conveyor belt on the west side of the residual vortex of typhoon "Likima". The environmental condition was characterized by weak vertical wind shear and strong low-level thermal instability. The Yingkou dual-polarization radar located 15 km away from the tornado detected the hook echo, the descending reflectivity core (DRC), the weak echo hole (WEH), and the tornadic debris signature (TDS) in mini supercell. The outflow of the old thunderstorm gust front moved westward, while the sea breeze front near Yingkou moved slowly eastward. The two boundary layer convergence lines meeting leaded the forming of γ-mesoscale vortex as horizontal shear instability. The outflow boundaries intersection, the ambient large positive buoyancy and the vertical perturbation pressure gradient associated with the low pressure induced by the middle level mesocyclone produced strong updraft. the collocating of the updraft with the γ-mesoscale vortex played a critical role for the genesis of misocyclone by strong stretching. The combination of the maximum rotation velocity and the minimum diameter of the misocyclone corresponded to the tornadogenesis, and the separation of the misocyclone and the mesocyclone in the middle level corresponded to the death of the tornado.
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