Occurrence of Narrow Bipolar Event as Part of Cloud-to-Ground Flash in Tropical Thunderstorms

Ahmad, Mohd Riduan and Mohd Esa, Mona Riza and Cooray, Vernon (2014) Occurrence of Narrow Bipolar Event as Part of Cloud-to-Ground Flash in Tropical Thunderstorms. In: International Conference on Atmospheric Electricity, 15-20 June 2014, Norman, Oklahoma, USA. (In Press)

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Abstract

This paper reports a recent observation of Narrow Bipolar Event (NBE) occurrence as part of cloud-to-ground flash activity in tropical thunderstorms. Electric field change measurement has been conducted in Southern Malaysia (latitude 1°34′12.00″N, longitude 103°38′42.00″E) during Northeastern monsoon season between November and December 2012. From the total 173 recorded NBEs, more than half, (60.7%), appeared to occur in isolation; that is, no other lightning flashes occurring prior to or following the NBEs within the record length of 500 ms with a 150 ms pre-trigger delay. The remaining 36.4% of NBEs have been observed to occur as part of cloud-to-ground flash activity. We found that more than one third of NBEs with cloud-to-ground flash, about 38.1% have occurred between return strokes. Both polarities of NBEs (+NBE and –NBE) were recorded between the return strokes. The other one third of NBEs, about 36.5% have been observed to follow the last return stroke with both polarities of NBEs were recorded. On the other hand, only about 25.4% of NBEs (both polarities) have been observed to occur prior the first return stroke. The range of time intervals between the NBEs and the first return strokes is from 19 to 158 ms. The range of ratios of –NBEs peak amplitudes to the first return stroke peak amplitudes is found to be much larger than +NBEs, between 0.3 and 3.8 for –NBEs when compared to 0.3 and 2.6 for +NBEs. Furthermore, we observed 5 events (4 +NBEs and 1 –NBE) where NBEs have preceded preliminary breakdown process (PBP) before the first return stroke. Interestingly, +NBEs have occurred at much shorter time intervals before the first pulse of PBP compared to –NBEs. The range of time intervals between the +NBEs and the first pulse of PBP is between 5.8 and 52 ms while for –NBE it is 115 ms.

Item Type: Conference or Workshop Item (Poster)
Subjects: Q Science > QC Physics
Divisions: Faculty of Electronics and Computer Engineering > Department of Computer Engineering
Depositing User: En. Mohd Riduan Ahmad
Date Deposited: 03 Jun 2014 01:27
Last Modified: 28 May 2015 04:25
URI: http://eprints.utem.edu.my/id/eprint/12492
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