内蒙古一次强龙卷天气的中尺度特征分析

Mesoscale Characteristics of a Strong Tornado Weather in Inner Mongolia

利用新一代多普勒天气雷达资料、逐5 min自动站资料、常规观测资料和NCEP(1°×1°)再分析资料等,采用NCEP格点资料内插到站点计算龙卷发生地物理量的方法,对2021年6月25日发生在内蒙古太仆寺旗的一次强龙卷过程进行分析研究。结果表明:龙卷发生在东北冷涡背景下,出现在低层的西南气流中。龙卷发生的环境场特征为上干冷下暖湿的不稳定大气层结,地面辐合线及干线为强对流提供了触发条件,低抬升凝结高度、强低层垂直风切变和大的对流有效位能为龙卷提供了有利条件。雷达回波表明,此次龙卷过程主要与3个超级单体风暴相关,这些单体有明显的钩状回波“、V”型缺口、旁瓣回波、回波悬垂的特征,雷达距离龙卷发生地超过100 km,未识别出龙卷涡旋特征,但在速度图上存在明显的气旋式辐合区。由风暴单体参数变化分析得出,龙卷发生前基于单体的垂直累积液态水有明显的跃增,在龙卷维持中回波顶高度、最大反射率因子及其高度都非常大。

Using data from the new generation Doppler weather radar,5-minute automatic station data,routine observation,and NCEP(1° × 1°) reanalysis data,physical amounts of tornado occurrence places were calculated by interpolating the NCEP grid data into the station.This study analyzed a tornado occurred on June 25,2021 in the Taipusi area of Inner Mongolia.The results showed that the tornado occurred under the background of a forward-dipping trough and appeared in the southwest airflow of the lower level.The environmental field of the tornado was characterized by an unstable atmosphere with upper dry and cold,and lower warm and wet conditions,with strong convection triggered by the convergence line and main line.Low lift condensation height,strong low-level vertical wind shear,and large convective effective potential energy provided favorable conditions for the tornado.The tornado process was caused by the interaction of several supercell storms.The analysis of radar echo data showed that the supercell had obvious hook echo,“V”notch,echo drape,and side lobe echo characteristics.The radar was over 100 kilometers away from the tornado and did not identify the characteristics of the tornado vortex,but there were obvious cyclonic convergence regions on the velocity map.The analysis of the change of the parameters of the storm monomer showed that the vertical accumulation of liquid water based on the monomer had a significant jump before the tornado occurred,and the echo top height,maximum reflectivity factor,and its height were very large during tornado maintenance.