2024年贵阳机场两次飑线过程的环境条件与雷达特征对比分析

Comparative Analysis of Environmental Conditions and Radar Characteristics of Two Squall Line Processes at Guiyang Airport in 2024

摘要: 基于ECMWF再分析资料、常规天气资料、探空资料、贵阳机场地面观测纪要栏资料、自观逐分钟资料以及雷达资料，对2024年贵阳机场两次飑线过程进行诊断分析，结果表明：两次过程均受西南涡影响，700 hPa西南急流造成低层动力结构不稳定；“上冷下暖”的垂直结构提供了热力不稳定条件；低层辐合、中层辐散的配置则提供了动力不稳定条件。K指数、SI指数、CAPE值均表明两次过程前贵阳上空存在大量不稳定能量；较大的SSI指数表明大风出现条件有利；较高的0℃层和−20℃层高度不利于冰雹产生。雷达回波显示两次过程均呈现明显的弓状回波特征，且低层出现速度辐合。两次过程不同点在于：在影响系统方面，4月18日过程受垂直槽东移及地面低压前部影响，7月1日过程则受前倾槽和地面辐合线影响。在水汽条件方面，7月1日700 hPa水汽通量值相对较弱。4月18日低层为东北偏南辐合，7月1日则为西北西南辐合，且零速度线风速梯度相对较大。

Abstract: Based on ERA5 reanalysis data, conventional weather data, sounding data, surface observation records from Guiyang Airport, minute-by-minute automatic weather station data, and radar data, a diagnostic analysis was conducted on two squall line events at Guiyang Airport in 2024. The results indicate that both events were influenced by a southwest vortex, with the 700 hPa southwest jet stream causing instability in the low-level dynamic structure. The “cold upper, warm lower” vertical structure provided thermal instability conditions, while the configuration of low-level convergence and mid-level divergence provided dynamic instability conditions. The K-index, SI index, and CAPE values all indicated the presence of substantial unstable energy over Guiyang before both events. The relatively high SSI values suggested favorable conditions for strong winds. The high altitudes of the 0˚C and −20˚C layers were unfavorable for hail formation. Radar echoes showed that both events exhibited distinct bow-echo characteristics, with velocity convergence observed at low levels. The differences between the two events are as follows: In terms of influencing systems, the April 18 event was affected by an eastward-moving vertical trough and the front of a surface low, while the July 1 event was influenced by a forward-tilting trough and a surface convergence line. Regarding moisture conditions, the 700 hPa water vapor flux on July 1 was relatively weaker. On April 18, low-level convergence was from the northeast-south direction, whereas on July 1, it was from the northwest-southwest direction, and the wind speed gradient along the zero-velocity line was relatively larger.