Beijing Broadband Lightning NETwork and the Spatiotemporal Evolution of Lightning Flashes during a Thunderstorm

The Beijing Broadband Lightning NETwork (BLNET) is a regional total flashes 3D (three-dimensional) location network that combines research and business. In 2015, the BLNET hardware, station network layout, and location algorithm were updated and upgraded to improve the sensitivity of the sensor and improve computational efficiency and detection performance. BLNET features the functions of IC (Intra-Cloud) flashes, CG (Cloud-to-Ground) flash-pulse-type identification, and current peak estimation, as well as 3D real-time location of lightning radiation pulses and the fine location of the channel-resolvable lightning discharge process. The analysis of the real-time 3D location results for the lightning radiation source pulse during the thunderstorm that occurred on 7 July 2017 shows a total of 11,902 lightning flashes during the thunderstorm process. Most of these flashes were dominated by IC flashes, with CG flashes accounting for just 28% of the total. PCG (Positive Cloud-to-Ground) flashes account for only 5% of the total number of CG flashes. During the mature period of the thunderstorm, the maximum lightning frequency was 927 flashes (6 min)⁻¹. By comparing and analyzing the location of the lightning radiation source and the radar echo at the corresponding time, the radiation source was found to be basically concentrated in the strong echo range. The fine location results of the PCG flashes indicate that the initial stage involved a clear pre-breakdown process. The origin of the lightning radiation source was about 5.4 km above sea level, and then the channel developed upward. At about 10 km, the channel began to exhibit a horizontal development. The fine location results of the NCG (Negative Cloud-to-Ground) flashes indicate that the discharge first originated from a height of about 7.1 km, then the channel developed to the south, and some negative pilot branches developed downward. After about 38 ms, the channel stopped developing for a short time. After 17 ms, the channel development began again and the air was re-energized. The above results show that BLNET can locate and monitor 3D real-time lightning activity of the whole thunderstorm life history, as well as obtain the fine location of the lightning 3D discharge channel.