Stability and Charging Characteristics of the Comma Head Region of Continental Winter Cyclones

This paper presents analyses of the finescale structure of convection in the comma head of two continental winter cyclones and a 16-storm climatology analyzing the distribution of lightning within the comma head. A case study of a deep cyclone is presented illustrating how upper-tropospheric dry air...

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Bibliographic Details
Published in:Journal of the atmospheric sciences 2014-05, Vol.71 (5), p.1559-1582
Main Authors: Rauber, Robert M, Wegman, Joseph, Plummer, David M, Rosenow, Andrew A, Peterson, Melissa, McFarquhar, Greg M, Jewett, Brian F, Leon, David, Market, Patrick S, Knupp, Kevin R
Format: Article
Language:English
Subjects:
Air
Aircraft
Case studies
Cells
Charging
Climatology
Clouds
Cold
Convection
Convective available potential energy
Convective cells
Cyclones
Dry air
Drying
Elevated
Graupel
Ice
Ice particles
Laboratories
Lakes
Lightning
Lightning flashes
Meteorology
Potential energy
Precipitation
Radar
Radar measurement
Snow
Storms
Stratiform clouds
Supercooled water
Thunderstorms
Updraft
Winter
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Summary:This paper presents analyses of the finescale structure of convection in the comma head of two continental winter cyclones and a 16-storm climatology analyzing the distribution of lightning within the comma head. A case study of a deep cyclone is presented illustrating how upper-tropospheric dry air associated with the dry slot can intrude over moist Gulf air, creating two zones of precipitation within the comma head: a northern zone characterized by deep stratiform clouds topped by generating cells and a southern zone marked by elevated convection. Lightning, when it occurred, originated from the elevated convection. A second case study of a cutoff low is presented to examine the relationship between lightning flashes and wintertime convection. Updrafts within convective cells in both storms approached 6-8 m s super(-1), and convective available potential energy in the cell environment reached approximately 50-250 J kg super(-1). Radar measurements obtained in convective updraft regions showed enhanced spectral width within the temperature range from -10 degree to -20 degree C, while microphysical measurements showed the simultaneous presence of graupel, ice particles, and supercooled water at the same temperatures, together supporting noninductive charging as an important charging mechanism in these storms.
ISSN:0022-4928
1520-0469
DOI:10.1175/JAS-D-13-0253.1