双偏振雷达在江苏“7.6”降雹过程中的应用分析
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1.苏州市气象局;2.中国气象科学研究院灾害性天气国家重点实验室;3.①苏州市气象局;4.②中国气象科学研究院灾害性天气国家重点实验室

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RESEARCH ON JIANGSU “7.6”HAIL EVENT BASED ON DUAL-POLARIZATION WEATHER RADAR APPLICATION
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1.Suzhou Meteorology Bureau;2.State Key Laboratory of Sever Weather Chinese Academy of Meteorological Sciences;3.China

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    摘要:

    本文针对2019年7月6日发生在江苏徐州、宿迁、淮安到南京和常州一线的一次大范围冰雹、局部并伴有雷暴大风和短时强降水的强对流天气过程,通过徐州和南京S波段双偏振雷达偏振参量分析及宿迁和淮安的双多普勒天气雷达风场反演技术对冰雹云的热动力结构和微物理特征开展了详细的分析。利用再分析资料分析此次过程的天气背景,不稳定机制、抬升条件。结果表明:此次大范围强对流天气发生在高空冷涡南掉、横槽南摆,槽线6日上半夜前自北向南扫过江苏全境,低层暖湿气流北抬,上下层强烈不稳定的环流背景下,地面有低压缓慢东移南压,提供了辐合抬升条件。江苏大部从地面至600hPaθse随高度减小的位势不稳定区和0-6km强垂直风切分别为大范围冰雹天气的发生提供强热、动力不稳定条件。此次降雹天气过程,雷达回波图上有典型的冰雹云特征:三体散射长钉、回波穹隆结构、强度超过50dBZ,中层径向辐合、风暴顶辐散等特征。双偏振雷达各偏振参量也表现出冰雹云的特点:出现冰雹的地区展现ZH 大、ZDR小、CC小的特征,ZDR值为-1.0-0.5dB,CC值小于0.85;超级单体在近地层还出现表征入流区的CC谷、ZDR柱、KDP柱等特征。ZDR柱、KDP柱和CC谷等双偏振参量特征在强对流短时临近预报和冰雹识别方面具有很强的应用潜力。双雷达风场反演表明此次过程降雹集中时段,冰雹云的穹隆空间结构,降雹时刻存在的明显下沉气流。

    Abstract:

    Based on the S-band dual polarization Doppler weather radar of Xuzhou and Nanjing, the single polarization radar of Suqian and Huaian, and the reanalysis data, this paper analyzes the circulation background, instability mechanism dynamic, uplift conditions, radar echo and the evolution characteristics of dual polarization radar parameters and the wind inversion technology of dual radar of a wide range hailstorm process accompanied by thunderstorm and short-term heavy rainfall occured in Jiangsu Xuzhou, Suqian, Huaian, Nanjing and Changzhou on July 6, 2019. The results show that the wide range strong convective weather occurred when the cold vortex falling on high level and horizontal trough swing south, the trough line swept across Jiangsu from north to south before midnight on the 6th,the lower layer warm and humid air flow moved northward,under the background of strong unstable circulation on upper and lower layers, and the low pressure slowly moved eastward and the South pressure provided the convergence and uplift conditions. The vertical dry and cold air over Jiangsu is superimposed on the warm and wet air flow, the convective instability layer where θse decreasing with height from ground to 600hPa and the strong vertical wind shear of 0-6km provide strong thermal and dynamic instability conditions for the process. The intensity of radar echo is generally over 50 dBZ, and the echo top is always above 10 km in this procedure. What's more, it appears a significant Three Body Scattering Spikes, cyclonic convergence and storm top divergence. Hail storm can be identified by the polarization parameters (such as ZDR, KDP, CC). Hail storm usually exist in the area with strong reflectivity、low value of ZDR, and CC. The typical value of ZDR is usually between -1.0 and 0.2 and the value of CC is less than 0.85. In addition, ZDR and KDP columns help to identify hail, thunderstorm, and short-term heavy rainfall. The characteristics of the above two polarization parameters have great potential in the application of strong convection short-term approach prediction and hail recognition. Using the double radar wind inversion technology to study the hail period, it is found that there is obvious downdraft in the hail period. The three-dimensional flow field structure of the hailstorm supercell is as follows: the cyclonic air flow in the front of the storm moves into the storm, then gradually inclines to the top of the storm to form the anticyclonic air flow, and gradually forms the downdraft; in the weakening stage of the system, there is a strong downdraft, strong echo bottom and ground. Dual radar can retrieve the fine structure of three-dimensional wind of hailstorm supercell, which is helpful to deepen the understanding of hailstorm cloud structure and improve the prediction and early warning ability of severe convective weather such as hail storm.

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  • 收稿日期:2020-11-16
  • 最后修改日期:2021-03-14
  • 录用日期:2021-03-18
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