江淮地区一次冰雹过程的双线偏振雷达观测分析

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

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ZDR<−0.5 dB,相关系数(ρhv)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(KDP)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ρhv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(ZH)、ρhv和反射率因子标准差(SD(ZH))概率密度分布与北美三体散射比较接近;ZDR分布更偏向于负值区域,差分相位标准差(SD(φDP))分布范围大约是北美结果的2倍。

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 ZDR(<−0.5 dB),lowρhv(~0.9)and negative KDP 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,andρhv 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 ZH,ρhv and(SD(ZH))within three-body scattering signature are similar to that in North American,and the PDD of ZDR tends to be more negative,while the range of distribution for SD(φDP)is about twice that in North America.