Analysis of initial breakdown pulse (IBP) generated by lightning flashes in tropical

Khor, Kelly (2024) Analysis of initial breakdown pulse (IBP) generated by lightning flashes in tropical. Project Report. Universiti Teknikal Malaysia Melaka, Melaka, Malaysia. (Submitted)

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Abstract

A thunderstorm characterized by intense lightning and heavy rainfall that led to a series flash flood which caused serious damage and the number of flood victims in Malacca. Therefore, it is crucial to understand the lightning initiation mechanism for improving forecasting and identifying lightning activity. This project presented two thunderstorms from Melaka reported during lightning activity to anlayze the characteristic of the initial breakdown pulses (IBP) of lightning waveform in 51 CG flashes and to evaluate the correlation between the lightning flashes and electric field when a flash flood happened in Melaka on 4th and 5th January 2022. In the analysis of the characteristic of breakdown pulses, IBP train were observed in 100% of the cases. Among 51 CG flashes, the arithmetic mean of the total pulse train duration was 6.47 ms and separation duration between the breakdown pulse and return stroke (IBP- FRS) as 38.76 ms. By observing on single pulses, the rise time (tr) to be 3.74 μs, zero crossing time (tz) as 13.38 μs. The AM value of the pulse durations (TPULSE) and interpulse intervals (IPT) were 27.79 μs and 92.54 μs, respectively. The ratio between the maximum peak amplitude of the IBP and the peak RS electric field was 42%. In other hand, the relationship between lightning and electric field during a thunderstorm that happened flash flood were investigated. The analysis focused on data collected by a FA and SA system recorded a total of 61 and 113 lightning flashes on 4 and 5 January, respectively. The lightning activity and electric field strength were highly correlated since the periods with the most lightning strikes also showed the strongest electric fields. On 4th January 2022, most lightning of 59 flashes and the highest electric fields observed of 7.22 kV/m occurred between17:00:00 and 19:59:59. Same for the storm on 5th January 2022, the electric field was higher observed was 6.1 kV/m at 16:08:44 with the range of time from 15:00:00 to 18:00:00 where the flash rate was higher with 65 flashes (57.52%) occurrence at the same time. It could be concluded that lightning flashes and EFM data indicate a strong correlation between the occurrence of major thunderstorms systems and electric field on a regional scale

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