一次隆冬大范围混合强对流潜势和物理量诊断分析

Diagnostic Analysis of Potential and Physical Quantities of Large-Scale Mixed Strong Convection in Deep Winter

摘要: 为进一步认识冬季混合强对流天气发生发展机制，本文利用常规气象观测资料、区域自动站资料、强天气监测资料以及NCEP 1˚ × 1˚ 6 h再分析资料计算的相关物理量资料，对2020年1月6日午后到上半夜贵州中东部大范围雷雨大风、冰雹、短时强降水等混合强对流天气过程的对流潜势和物理量进行诊断分析。结果表明：西北太平洋副热带高压显著偏强偏西偏北，西南低空急流强盛，与高空急流形成耦合形势，为大范围强对流天气的发生发展提供了暖湿不稳定背景和动力抬升条件。强对流天气发生前，地面热低压强烈发展加深，辐合锋生加强，本地出现异常增温增湿降压现象，边界层积聚大量不稳定能量。500 hPa温度槽超前的南支槽东移，高空冷平流入侵与低层低涡切变线、地面辐合线共同触发不稳定能量强烈释放，是此次大范围混合强对流天气的触发机制。强对流发生前垂直风切变、水汽辐合和动力辐合及高低空冷暖平流均显著加强。强对流天气出现在低空急流加强到最强盛时期、高低空冷暖平流达到最强之后，强对流发生在850 hPa切变线南侧、低空急流左侧强水汽辐合区和地面辐合线附近。

Abstract: In order to further understand the occurrence and development mechanism of winter mixed severe convective weather, relevant physical data were calculated by using conventional meteorological observation data, regional automatic station data, strong weather monitoring data and NCEP 1˚ × 1˚ 6 h reanalysis data. The convective potential and physical quantities of the mixed severe convective weather process from the afternoon to the early night of January 6, 2020 in central and eastern Guizhou, including thunderstorms, hail and short-time heavy precipitation, were analyzed. The results show that the subtropical high over the northwest Pacific Ocean is significantly stronger than that over the northwest Pacific Ocean, and the low-level southwest jet is strong and strong, forming a coupling situation with the upper-level jet, providing a warm and humid unstable background and dynamic lifting conditions for the occurrence and development of large-scale severe convective weather. Before the occurrence of severe convective weather, the surface thermal low pressure developed strongly and deepened, convergence frontogenesis strengthened, local abnormal warming, humidification and depressurization occurred, and the boundary layer accumulated a lot of unsta-ble energy. The triggering mechanism of this large-scale mixed severe convective weather was the south branch of the 500 hPa temperature trough moving eastward in advance, the invasion of cold advection in the upper air, the vortex shear line in the lower layer and the convergence line on the ground. The vertical wind shear, water vapor convergence and dynamic convergence, and advection at high and low altitudes were significantly strengthened before the strong convection occurred. The strong convective weather occurred on the southern side of the 850 hPa shear line, the convergence of strong water vapor on the left side of the low-level jet and near the surface convergence line.