基于风廓线雷达的贵州中部一次强对流天气特征分析

Analysis of a Severe Convective Weather in Central GuizhouProvince Based on Wind Profiler Radar

【目的】为了分析风廓线雷达对强对流的探测能力及临近预警指标。【方法】利用风廓线雷达基本和反演参量及常规气象资料,对2023年3月16日贵州中部大范围混合性强对流天气进行分析。【结果】此次过程是在高空槽、低层切变线、低空急流及有利的环境条件共同作用下,由地面辐合线和冷锋先后触发形成的。风廓线雷达水平风场能探测槽线、切变线及地面冷空气的准确过境时间及低空急流的变化,较常规地面和高空资料优势明显。【结论】(1)风廓线雷达反演的温度平流、垂直风切变产品可以反映降雹区周边环境的层结不稳定和低层较强垂直风切变特征以及强降水发生时强冷平流入侵和整层深厚强垂直风切变特征,低空急流指数跃增后消失指示了短时强降水的发生。(2)垂直速度≥4 m·s-1、谱宽≥1 m·s-1、大气折射率结构常数C_n2≥-130 dB,信噪比SNR≥50 dB可作为划分有无降水的界限,且垂直速度和谱宽的伸展高度有助于区分对流性和稳定性降水阶段。

Based on the basic and retrieved parameters of wind profiler radar and the conventional meteorological data,the mixed severe convection weather that occurred in the central part of Guizhou Province on March 16,2023,is analyzed so as to explore the detection capability of wind profiler radar for severe convection and the nowcasting warning index.The results show that:(1)This process was triggered by the surface convergence line and the cold front under the joint action of upper trough,low-level shear line,low-level jet stream and favorable environmental conditions.The horizontal wind field of wind profiler radar can reflect the accurate transit time of trough line,shear line and surface cold air,as well as the changes of low-level jet streams,so it has obvious advantages over the conventional surface and high-altitude data.(2)The temperature advection and vertical wind shear products retrieved by wind profiler radar can reflect the stratification instability and strong vertical wind shear characteristics in the surrounding environment of hail area,and can also reflect the characteristics of strong cold advection intrusion and deep-strong vertical wind shear in the integrated atmosphere during the process of severe precipitation.The disappearance of low-level jet index after a sudden increase indicates the occurrence of the short-time severe precipitation.(3)Vertical velocity≥4 m·s-1,spectral width≥1 m·s-1,refractive index structure constant(C 2 n)≥-130 dB,and signal-to-noise ratio(SNR)≥50 dB can be used as the signals to distinguish whether there is precipitation or not.Besides,the heights of vertical velocity and spectral width are helpful to distinguish convective precipitation stages from stable precipitation stages.