一次新生脉冲风暴分析

本文利用多普勒天气雷达、地面自动站等高时空分辨率观测资料和NCEP1×1°再分析资料,对2017年7月28日南充市区由脉冲风暴引起的局地强对流天气的背景、环境条件、雷达特征、大风成因等进行了研究和探讨。结果表明:(1)此次强对流天气过程以受西太平洋副热带高压控制为背景,有异常强的对流不稳定能量和十分充足的水汽;边界层切变线与弱冷空气回流进入盆地东北部及下垫面加热不均匀导致的强温度梯度是风暴新生的触发机制;在弱垂直风切变的环境条件下,使得过程中雷暴具有脉冲风暴特征。(2)此次过程有多个脉冲风暴的活动,造成南充城区大风的脉冲风暴主要有两个,1号风暴单体在强的温度梯度触发后,快速向上向下发展,成熟崩塌时以下击暴流的形式形成强的地面辐散气流,造成高坪站大风;强的下沉气流到达地面形成冷中心,冷中心与前方的暖中心形成强的温度梯度即冷池密度流,冷池密度流产生强的气压梯度力风,再叠加单体下层辐散气流造成了华凤镇的极端大风。 

Case Analysis of a Newborn Strong Thunderstorm

In this paper, by using doppler weather radar, ground data observed by automatic station high space-time resolution and NCEP1 x 1 ° reanalysis data, on July 28, 2017 in Nanchong city of local strong convective weather caused by pulse storm background, environmental conditions, characteristics of radar observations and wind formation are studied and discussed.Resultsshow that: This severe convection event under the control of the western Pacific subtropical high, have unusually strong convective instability energy and sufficient ambient moisture, which provides very good conditions for the development of the convective storm. Boundary layer shear line and weak cold air flowing into the basin in the northeast and temperature gradient caused by uneven heating are triggering new storm. In the environment of weak vertical wind shear, thunderstorms in the process are characterized by pulsed storms. There are several pulse storms in this process and two main pulse storms causing strong wind in Nanchong city. After the strong temperature gradient triggered, storm monomer no.1 develops rapidly upward and downward. When it is mature and collapses, a downburst occurs, causing high wind at Gaoping station. A strong downdraft reaches the surface to form a cold center, The center of the cold and the warm core ahead form a strong temperature gradient called the cold pool density flow.The density flows create a strong pressure gradient, which overlays onto the divergent airflow in the lower layer, causing the extreme wind in the town of huafeng.