Statistical analysis on preliminary breakdown pulses in negative cloud-to-ground flashes occurred in Colombia

Abstract

In this paper, a characterization of preliminary breakdown pulse trains (PBP trains) preceding the first return stroke (FRS) in 76 negative cloud to ground (-CG) lightning flashes occurred in Bogota, Colombia (tropical region located above 2500 meters of altitude) is presented. For the measurement campaign, a broadband parallel-plate antenna system was used with a 500 ms full observation window and a pre-trigger time of 250 ms. After execution a statistical analysis, several results were obtained. The geometric mean (GM) and the arithmetic mean (AM) of the time interval between the largest peak of the PBP train and the maximum value of the FRS (PBP - FRS interval) was 1.08 ms and 1.39 ms, respectively. In addition, the AM of pulse train duration and the ratio between the peak value of the PBP train and its FRS (PBPmax/FRS ratio) were 1.39 ms and 0.55 p.u., respectively. Finally, the number of pulses of the PBP trains characterized were located in the range of 3 to 72 pulses.