江淮地区一次冰雹过程的双线偏振雷达观测分析

为了进一步认识冰雹和三体散射的双线偏振雷达观测特征，提高业务预警能力和奠定基于双线偏振雷达的地面降雹识别基础，利用南京双线偏振雷达观测资料，统计分析了2019年3月20日冰雹过程发展、成熟和降雹阶段的观测特征及微物理过程。结果表明:（1）雹暴在成熟阶段具有高悬的强回波中心和较高的顶高，强回波中心差分反射率Z_DR＜?0.5 dB，相关系数（ρ_hv）约为0.9，由于冰雹后向散射相位的影响，该区域比差分相位（K_DP）呈现负值，指示了该区域有冰雹存在，并被相态分类算法（HCA）正确识别；（2）降雹阶段，高层反射率因子减小，强回波中心下降到地面附近，融化层以下ρ_hv增大，指示高层下落的冰相粒子整体尺寸减小；HCA识别到冰雹开始减少时，地面观测到冰雹；（3）三体散射的反射率因子（Z_H）、ρ_hv和反射率因子标准差（SD（Z_H））概率密度分布与北美三体散射比较接近；Z_DR分布更偏向于负值区域，差分相位标准差（SD（φ_DP））分布范围大约是北美结果的2倍。 

An analysis of a hail case over the Yangtze and Huai River Basin based on dual-polarization radar observations

In order to better understand the hail and three-body scattering signature, improve the ability of operational warning and lay the foundation of automatic hail identification on the ground based on dual-polarization radar, a hail case observed by the S-band polarimetric radar on 20 March 2019 is used to examine the observational signature and microphysical process. The result shows that: (1) During the mature stage, the hailstorm has high echo top and strong echo area aloft that are characterized by negative Z_DR (＜?0.5 dB), low ρ_hv (~0.9) and negative K_DP caused by backscattering phase, indicating that hails existing within this area are reasonably identified by HCA; (2) during the period of hail falling on the ground, the reflectivity in high levels decreases, the strong echo area descends close to the ground, and ρ_hv below the melting level increases, indicating that the size of ice particles falling from high levels decreases; hails fall to the ground at the time when the hails identified by HCA is decreasing; (3) the probability density distributions (PDD) of Z_H, ρ_hv and (SD (Z_H)) within three-body scattering signature are similar to that in North American, and the PDD of Z_DR tends to be more negative, while the range of distribution for SD (φ_DP) is about twice that in North America.