Phenomenology and characterization of multiple ground contact strokes in natural lightning

Leandro Z.S. Campos, Antonio C.V. Saraiva, Kenneth L. Cummins, Larissa Antunes, Osmar Pinto Junior, Dailton G. Guedes

Research output: Contribution to conferencePaperpeer-review

Abstract

An analysis of the phenomenology and overall characteristics of 35 cloud-to-ground (CG) strokes that create two or more contact points to the ground in a millisecond scale are presented. This dataset includes both the “classical” forked strokes (first observed in streak camera records) and the new class of this type of phenomenon, called “upward illumination” strokes, introduced in more recent works. The broad class of strokes that present two or more contact points in a millisecond and sub-millisecond scale was termed “multi ground contact strokes” (MGCS) as their geneses are very similar: one branch from the main trunk of a stepped leader produces a second stroke shortly after the first return stroke occurs. Over a five-day campaign, a total of 357 negative CG flashes were recorded by the RAMMER network, which is comprised of four high-speed video cameras (three stationary monochromatic and one mobile colored). They were set up for recording with 1200 x 500 pixels per frame, at 2500 frames per second (390-µs exposure time). From careful visual inspection, 35 MGCS events were found, among which 22 were classified as forked strokes and 13 as UI strokes. RAW data from BrasilDAT network was used to identify and give additional information about the MGCS. After a number of detailed case studies and a review of the recent literature, it was found that the main difference between UI and classical forked stroke events are: a) UI stroke channels present an optical discontinuity from the main trunk during its development (i.e., there was a region of lower or no apparent luminosity between its brighter region and the forking point from the main channel), b) the time between strokes is longer than in the case of classical forked strokes and c) the peak currents of the UI strokes are, usually, very small. Analysis of the relationship between the interstroke interval and peak current added new information on the physical characteristics and distinctive features of UI and forked strokes.

Original languageEnglish (US)
StatePublished - 2014
Externally publishedYes
Event15th International Conference on Atmospheric Electricity, ICAE 2014 - Norman, United States
Duration: Jun 15 2014Jun 20 2014

Conference

Conference15th International Conference on Atmospheric Electricity, ICAE 2014
Country/TerritoryUnited States
CityNorman
Period6/15/146/20/14

ASJC Scopus subject areas

  • Atmospheric Science
  • Geophysics

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