摘要:受东北冷涡与副热带高压西北部暖湿气流影响，2015年7月27日北京地区爆发了一次具有明显对流单体合并特征的强飑线灾害性强对流天气过程。利用北京闪电定位网（BLNet）总闪定位、多普勒雷达和探空资料等，详细分析了此次飑线过程整个生命史期间不同对流区的总闪活动特征。结果表明，整个飑线过程以云闪为主，地闪活动以负地闪为主；对流单体合并时云闪数量激增，飑线过程后期正地闪比例跃增。93%的闪电主要分布在距对流线10 km范围内，层云区闪电较少；层云区的闪电电荷来源主要是由对流区的电荷经过过渡区输送而来，正地闪更易发生在过渡区和层云区。对流合并过程中有大量的水汽集中，垂直积分液态含水量（VIL）峰值超前闪电峰值24 min。利用变分多普勒雷达分析系统（VDRAS）对这次过程的三维风场进了反演，据此对单体合并期间闪电增强的动力原因进行了研究。根据VDRAS反演的动力场来看，对流云单体合并主要发生在低层辐合区内，合并后上升运动加强，上升气流范围变大，闪电活动显著增强，并主要发生在具有较强垂直风切变的区域，少部分闪电发生在对流区后部开始出现下沉气流的区域。
关键词:飑线/
闪电/
对流区/
层云区/
对流合并
Abstract:Influenced by the Northeast China cold vortex and warm and moist airflow in the northwestern part of the subtropical high, a damaging squall line with cell merging process took place in Beijing area on 27 July 2015. Based on data from Beijing Lightning Network (BLNet), S-band Doppler radar observations, and radiosonde data, the characteristics of total lightning activity associated with this severe squall line are analyzed. The results show that the lightning activities generated by the squall line were mainly IC (intra-cloud) lightning flashes; CG (cloud-to-ground flashes) were dominated by NCG (negative CG); in the dissipation stage, the ratio of PCG/CG (positive CG to CG) increased sharply. About 93% of total lightning flashes were distributed within 10 km distance of the convection line, while flashes occurring in the stratiform region were relatively fewer. PCG was more likely to occur in the transition zone and stratiform region; the occurrence of lightning in the stratiform region might result from the advection of charged particles from convective region through transition zone. There existed a large amount of water vapor concentration during the convection merging, and the peak of lightning lagged 24 minutes behind the peak of vertically integrated liquid water content (VIL). The Variational Doppler Radar Analysis System (VDRAS) is used to retrieve the three-dimensional wind field during the squall line process, and the reasons for the increase in lightning during the merging process are studied. According to the wind field retrieved from the VDRAS, the merging of convective clouds mainly occurred in the lower convergence zone; after the convection merging, the extent and intensity of the updraft both became intense, and the lightning activity became more active. Lightning was mainly concentrated in the region with strong vertical wind shear, while a small fraction of flashes occurred in the rear of the convection zone where downdrafts were observed to appear.
Key words:Squall line/
Lightning/
Convection zone/
Stratiform zone/
Cell merge
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