Luminosity in the initial breakdown stage of cloud‐to‐ground and intracloud lightning

We present simultaneously measured luminosity and electric field data from the initial breakdown (IB) stage in seven cloud‐to‐ground (CG) and eight intracloud (IC) lightning discharges along with, in three cases, radar and Lightning Mapping Array (LMA) data. The data were taken in north‐central Flor...

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Bibliographic Details
Published in:Journal of geophysical research. Atmospheres 2016-02, Vol.121 (3), p.1236-1247
Main Authors: Wilkes, R. A., Uman, M. A., Pilkey, J. T., Jordan, D. M.
Format: Article
Language:English
Subjects:
Breakdown
Delay
Electric discharges
Electric fields
Geophysics
initial
Lightning
Luminosity
Meteorology
Time resolved
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Summary:We present simultaneously measured luminosity and electric field data from the initial breakdown (IB) stage in seven cloud‐to‐ground (CG) and eight intracloud (IC) lightning discharges along with, in three cases, radar and Lightning Mapping Array (LMA) data. The data were taken in north‐central Florida in 2013 and 2014. Seven CG discharges had an arithmetic mean (standard deviation, SD) IB stage luminosity pulse train duration of 3 ms (2 ms), and within the seven CG discharges, 30 luminosity pulses had the following means (SD): 10% to 90% risetime 25 µs (16 µs), full width at half maximum 68 µs (21 µs), and delay between onset of the electric field pulse and associated luminosity pulse 8 µs (8 µs). Eight IC discharges had a mean (SD) IB stage luminosity pulse train duration of 11 ms (4 ms), and within the 8 IC discharges, 37 luminosity pulses exhibited mean risetimes, widths, and delays of 59 µs (36 µs), 176 µs (70 µs), and 34 µs (20 µs), all significantly greater than in the CG case. The roughly 10 LMA sources associated with each of the three IB stages in 2014 are grouped horizontally within about 1 km2. The mean altitude (SD) of the LMA points during two CG IB stages is 5 km (600 m) and 4.3 km (250 m) and during one IC discharge is 6.2 km (550 m). We discuss the role of optical scattering in delaying and distorting the observed luminosity waveforms. Key Points First adequately time resolved measurement and comparison of IB luminosity in CG and IC lightning Luminosity IB pulses lag electric field IB pulses by a mean 8 µs (CG) and 34 µs (IC) Characteristics of luminosity in IC discharges are different than those in CG discharges
ISSN:2169-897X
2169-8996
DOI:10.1002/2015JD024137