基于多源探测资料的“4.12”非典型冰雹特征分析

针对2020年4月12日发生在江苏苏州的一次大范围雷暴大风、局部伴有冰雹的强对流天气过程，基于常州S波段双线偏振多普勒天气雷达、湖州和青浦的单偏振雷达以及再分析资料，详细分析了此次过程的天气背景，不稳定机制、抬升条件和雷达回波及双偏振雷达参量演变特征，并结合双雷达风场反演技术分析超级单体的动力结构及云物理机制。结果表明此次过程发生在高空冷涡南掉、横槽南摆，上下层强烈不稳定的环流背景下，地面有辐合线提供了触发条件。苏南地面附近至600 hPa为θ_se随高度减小的对流不稳定层和0~6 km强烈的垂直风向切变分别为此次过程提供强热力和动力不稳定条件。此次降雹天气过程，雷达回波强度超过50 dBZ，有明显的三体散射、气旋式辐合、高层回波悬垂和强风暴顶辐散等特征；但是VIL和ET都很小，呈现非典型冰雹特征。双线偏振雷达各偏振参量(差分反射率Z_DR、差分相移率K_DP和相关系数CC)也都反映出冰雹云的典型特征:在Z_H大、Z_DR小、CC小的区域出现冰雹，Z_DR值通常为-1.0~0.2 dB，CC值普遍小于0.85。上述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。利用双雷达风场反演技术对降雹时段研究，发现1~5 km各层高度的风垂直切变、辐合的存在，有利于超级单体的发展和加强。双雷达能较好地反演雷暴大风的三维风场精细结构，有助于加深对冰雹云结构的认识进而提高冰雹等强对流天气的预报预警能力。 

CHARACTERISTIC ANALYSIS OF"4.12"ATYPICAL HAIL BASED ON MULTI-SOURCE DATA

Based on the Changzhou S-band dual polarization Doppler radar, the single polarization radar in Huzhou and Qingpu and reanalysis data, this paper analyzed the weather background, instability mechanism, uplift conditions, radar echo and dual polarization radar parameters evolution characteristics of the convective process on April 12, 2020 in Suzhou, Jiangsu Province. The dynamic structure and cloud physics of supercell were analyzed by using wind field retrieval technique of dual radar. The results showed that this process occurred under the background of high-altitude cold vortex falling to the south, transverse trough swinging to the south and strong instability of the upper and lower layers. The convective unstable layer where θ_se decreased with height and the strong vertical wind shear of 0~6 km provided strong thermal and dynamic unstable conditions for this process, respectively. During the hail process, the radar echo intensity exceeded 50 dBZ, with obvious characteristics of three-body scattering, cyclonic convergence, high-level echo overhang and severe storm top divergence; however, the VIL and ET were very small, showing the characteristics of atypical hail. The polarization parameters including differential reflectivity Z_DR, differential phase shift rate K_DP and correlation coefficient CC of dual line polarization radar also reflected the typical characteristics of hail cloud: hail appeared in the area with large Z_H, small Z_DR and small CC; the Z_DR value was usually -1.0~0.2 dB, and the CC value was generally less than 0.85. The above-mentioned features of dual polarization parameters have great application potential in the short-term nowcasting of severe convection and hail identification. It is found that the existence of convergence and vertical wind shear at the height of 1~5 km is conducive to the development and strengthening of supercell. Dual radar can well retrieve the fine structure of the threedimensional wind field of thunderstorm and gale, which will help deepen the understanding of hail cloud structure and improve the forecast and early warning of severe convective weather such as hail.