An analysis of the initial breakdown pulse for positive cloud-to-ground flashes

In order to further understand the initiating mechanism of positive cloud-to-ground (PCG) flashes, the nature and temporal characteristics of the positive breakdown pulse trains are investigated by electric field data in Conghua of Guangdong province. Considering the difference between the initial polarity of initial breakdown pulses and the first return stoke (RS), three types of bipolar pulse trains, including the same polarity, the opposite polarity and the both polarity, are identified. The percentages are 83.5%, 10% and 5.5%, respectively. The statistic results show that PCG flash with breakdown pulse trains, which occur when the amount of PCG flash is little, is about 11.6% of the total PCG flashes. The average time interval between the peak of adjacent pulses and pulse duration are 270.99 μs and 25.01 μs, respectively. The mean value of pulse train duration and the interval between PBP train and RS is 8.88 ms and 98.48ms, respectively. The average ratio of all samples between the maximum amplitude of pulse train and the amplitude of the first stroke pulse is 0.16. The ratio is smaller in of Guangzhou province than in Hokuriku coast in Japan.