基于C波段双偏振雷达一次强对流过程观测分析

Observational Analysis of a Severe Convective Event Using C-Band Dual-Polarization Radar

摘要: 利用贵阳龙洞堡国际机场C波段双偏振天气雷达资料和ERA5再分析资料，对2025年5月4日贵州省西北部一次伴有冰雹大风灾害性天气过程(简称“05·04”过程)天气背景和双偏振雷达回波参数演变进行分析。结果表明：在对流天气的酝酿阶段，高空槽系统引导中高层干冷空气向南推进，与低层持续输送的暖湿偏南气流形成显著交汇，从而构成了“上冷下暖”的热力不稳定层结，这为强对流的发生奠定了关键的大尺度环流背景。随后，在地面中尺度辐合线的动力抬升作用下，区域内积聚的大量不稳定能量被迅速释放，推动对流风暴快速生成并增强。雷达观测显示，反射率因子图上强回波区呈现典型的钩状形态，并伴有清晰的V型缺口和弱回波区结构。其中，强度超过50 dBz的强回波垂直伸展高度达到10公里以上，表现出强风暴单体的显著特征。上述雷达回波形态与垂直结构共同指示，该风暴具备产生冰雹和大风等强对流天气的充分条件。双偏振参量显示低仰角反射率因子$Z_h$ 大值区与$Z_{DR}$ 零值附近、$K_{DP}$ 大值区对应融化冰雹和大雨滴混合特征显著。

Abstract: Utilizing observation data from the Guiyang Longdongbao International Airport C-band dual-polarization weather radar and ERA5 reanalysis data, this study analyzes the synoptic background and the evolution of dual-polarization radar echo parameters associated with a severe convective weather event characterized by hail and damaging winds (referred to as the “05·04” event) that occurred in northwestern Guizhou Province on 4 May 2025. The results indicate that during the incipient stage of the convective event, an upper-level trough system steered dry and cold air from the mid-upper levels southward. This airflow significantly converged with the persistent warm-moist southerly flow at lower levels, establishing a thermodynamic instability characterized by a “cold-over-warm” stratification. This configuration provided the crucial large-scale circulation background for the development of severe convection. Subsequently, forced by the dynamic lifting of a surface mesoscale convergence line, the substantial unstable energy accumulated in the region was rapidly released, triggering the quick initiation and intensification of convective storms. Radar observations revealed that the area of intense reflectivity on the plan position indicator (PPI) displayed a typical hook echo morphology, accompanied by a distinct V-notch and a weak echo region (WER). Notably, the strong reflectivity cores exceeding 50 dBz extended vertically above 10 km, exhibiting the hallmark characteristics of a vigorous storm cell. The combined radar echo morphology and vertical structure collectively indicated that this storm possessed the necessary conditions for producing severe convective weather, including hail and damaging winds. Dual-polarization parameters showed that the area of high reflectivity ($Z_h$ ) at low elevation angles corresponded to regions with differential reflectivity ($Z_{DR}$ ) near zero and high specific differential phase ($K_{DP}$ ), signifying a significant mixture of melting hail and large raindrops.