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河南一次伴有龙卷的多阶段强对流天气形成机制分析

Formation mechanism of a multi-stage severe convective weather event accompanied by local tornado in Henan

  • 摘要: 利用常规观测资料以及区域自动站、卫星、新一代天气雷达和ERA5再分析等高时空分辨率资料,对2022年6月13日河南一次伴有局地龙卷的多阶段强对流过程(以下简称“6.13”过程)的环流形势、中尺度系统演变特征进行了分析,并探讨了该过程不同阶段对流触发维持机制以及濮阳局地龙卷的雷达监测特征。结果表明:(1) 这次东北冷涡槽后西北气流形势下大范围强对流天气具有影响范围广、持续时间长、灾害天气种类多的特点。(2) 雷达监测到该过程强对流系统分3个阶段相继经过河南,各阶段强回波均持续8~9 h,移速30~50 km·h-1,强对流系统以多单体为主,受西北气流引导自西北向东南方向移动且落区有重叠。(3) 河南上空始终维持强条件不稳定层结和中等到强的垂直风切变是“6.13”过程多阶段强对流天气长时间维持的重要原因。第一阶段河南本地强对流主要是由风场日变化、局地冷空气活动和地形分布共同作用形成的边界层辐合线或辐合中心触发;第二、三阶段强对流则由前期或同期周边区域强烈发展的地面中尺度雷暴高压伴随的阵风锋(出流边界)触发。(4) 濮阳县局地龙卷由发展迅速的超级单体产生,该单体回波生成后12 min出现钩状回波和中尺度气旋性涡旋、18 min出现龙卷涡旋特征(TVS),且钩状回波和中尺度气旋性涡旋较龙卷发生有6 min的提前量。

     

    Abstract: Henan encountered a multi-stage severe convective weather event (hereinafter referred to as "6.13" event) accompanied by local tornado on 13 June 2022. Using conventional observation data, regional automatic weather station data, satellite cloud images, Doppler weather radar data, ERA5 reanalysis data and other relevant data, we conducted an analysis on atmospheric circulation environment and the evolution characteristics of mesoscale systems for the "6.13" event. In addition, we discussed the initiation and maintenance mechanisms of convection in the different periods of this event and the radar characteristics of the local tornado in Puyang of Henan. Results are as follows. (1) The "6.13" event occurs under the northwest airflow behind the northeast cold vortex trough, and it is characterized by wide impact range, long duration and multiple types of disaster weather. (2) Radar detection results show that the severe convective systems in the "6.13" event passed through Henan in three periods one after another, and strong echoes in each period lasts for 8-9 hours, with the moving speed of 30-50 km·h-1. Most of the severe convective systems are multi-cells that all moved from northwest to southeast, with some of their areas overlapping under the guidance of northwest airflow. (3) Maintenance of the strong conditional instability and the moderate to strong vertical wind shear over Henan is an important cause for multi-stage severe convective weather in the "6.13" event lasting for a long time. The first period of local severe convection in Henan is mainly triggered by the convergence line or convergence center in the boundary layer formed by the combined effect of daily changes of wind field, local cold air activity, topographic distribution, while the second and third periods of severe convection are triggered by the gust front or outflow boundary accompanied by the surface mesoscale thunderstorm high formed by the strong developing convection systems in the surrounding area in the previous period or the same period. (4) The local tornado in Puyang is generated by a rapidly developing supercell storm. The hook echo and mesoscale cyclonic vortex appear 12 minutes after this supercell storm, and the tornado vortex characteristics (TVS) appear 18 minutes later. The hook echo and mesoscale cyclonic vortex are 6 minutes ahead of the occurrence of tornado, which can provide a reference information for early warning local tornadoes.

     

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