冷涡背景下致灾双飑线的触发和维持机制分析

The Trigger and Maintenance Mechanism of Disaster Causing Double Squall Lines under Cold Vortex Background

摘要:

利用区域自动站资料、ERA5再分析资料、FY-4A资料和多普勒雷达资料等，分析了2022年6月13日影响山东的双飑线过程的天气背景、环境条件、触发机制和发展维持原因。结果表明：（1）这次强对流过程是在高空冷涡背景下，由山东本地发展型飑线（简称飑线A）和山西河北生成后移入山东型飑线（简称飑线B）接连影响产生的，冷涡后部强盛的西北气流携带干冷空气与低层暖脊叠置，形成强的热力不稳定层结，同时有效位能和总指数较大，为飑线的发生提供了较好的环境条件。（2）鲁西北地面辐合线、850 hPa干线及渤海对流风暴南侧阵风锋是飑线A初始对流的触发机制，飑线B的触发与地面副冷锋以及太阳辐射加热有关。（3）垂直方向上系统前沿暖湿入流斜升到风暴顶产生辐散，后侧下沉气流则在飑线前侧产生辐合，而水平方向上表现为环境入流和风暴出流相互依存并错开的自组织结构，使得飑线A在山东北部弱垂直风切变条件下发展维持。鲁中山区以南地区水汽能量条件有利于飑线A下山维持发展，后侧层状云区范围增大。（4）飑线A影响豫东至鲁西南后，低层对流条件的快速重建和中等强度垂直风切变为后期飑线B的维持提供了有利的条件。

Abstract:

Using regional automatic station data, ERA5 reanalysis data, FY-4A data, and Doppler radar data, the weather background, environmental conditions, trigger mechanism, and evolution causation of the Shandong double squall line process on June 13, 2022 were analyzed. The results showed that: 1) This strong convective process was generated by the influence of two consecutive squall lines under cold vortex background, by the continuous influence of a locally developed squall line in Shandong (squall line A) and the squall line generated in Shanxi and Hebei that moved into Shandong (squall line B). The strong northwest airflow behind the cold vortex carried dry and cold air overlaid on the low-level warm ridge, establishing a strong thermal instability layer. The environment had large CAPE and total index, providing favorable environmental conditions for the occurrence of squall lines. 2) The surface convergence line in the northwest of Shandong, the 850 hPa dry line, and the gust front on the southern side of the Bohai convective storm were the triggering mechanisms of the initial convection of squall line A. The triggering of squall line B was related to the surface sub cold front and solar radiation heating. 3) In the vertical direction, the warm and humid inflow at the front of the system rose diagonally to the top of the storm, causing divergence, while the sinking airflow at the back converged in front of the squall line.In the horizontal direction, it exhibited a self-organizing structure where environmental inflow and storm outflow were interdependent and staggered, allowing squall line A to develop and maintain under weak vertical wind shear conditions in northern Shandong. The water vapor and energy conditions in the southern region of Mid-Shandong were conducive to the maintenance and development of squall line A, and the range of the posterior stratiform cloud area increases. 4) After the impact of squall line A from eastern Henan to southwestern Shandong, the rapid reconstruction of low-level convective conditions and moderate vertical wind shear provided favorable conditions for the maintenance of squall line B in the later stage.