Lightning Activity of a Severe Thunderstorm with Several Hail-Fall Stages in Beijing Metropolitan Region

Influenced by the Northeast China cold vortex and warm-moist airflow in low level, a damaging thunderstorm with five hail-fall stages occurred in Beijing on 10 June 2016. Based on the 3D-location results of total lightning from Beijing Lightning Network (BLNET) and Doppler radar data during the STORM 973 (Dynamic–microphysical–electrical Processes in Severe Thunderstorms and Lightning Hazards) campaign in 2016, the characteristics of lightning activity and radar reflectivity structure during this thunderstorm were analyzed. The thunderstorm consisted of three isolated cells triggered in sequence and finally merged together. The total lightning frequency increased significantly during the four analyzed hail-fall stages, up to 179 flashes min^?1. IC (intra-cloud) lightning flashes accounted for more than 80% of the total lightning. The ratio of PCG (positive cloud-to-ground) to CG (cloud-to-ground) lightning (PCG/CG) increased sharply before three hail-fall stages, by up to 58%. During the hailstorm developments, the area of radar echo greater than 45 dBZ increased, and the echo top exceeded 13 km. Lightning radiation sources mainly distributed in the altitude layer from 6 km to 10 km throughout the hailstorm process, which was consistent with a strong radar echo region. Moreover, the total lightning flashes increased dramatically before the three analyzed processes and passed the 2σ threshold test. Three of them were 8–18 minutes ahead of the hail-fallings, which shows that the total lightning frequency has a certain early warning ability for hail-fall processes.