HR: 17:30h
AN: AE44A-08    [Abstracts]
TI: Hydrometeor Environments Near Lightning Centroids and the Impact on Initial Breakdown
AU: * Bitzer, P M
EM: bitzerp@uah.edu
AF: University of Alabama in Huntsville, 301 Sparkman Dr., Huntsville, AL 35899, United States
AU: Christian, H
EM: hugh.christian@nsstc.uah.edu
AF: University of Alabama in Huntsville, 301 Sparkman Dr., Huntsville, AL 35899, United States
AU: Latham, J
EM: latham@ucar.edu
AF: National Center for Atmospheric Research, MMM Division, P.O. Box 3000, Boulder, CO 80307, United States
AB: One of the unanswered questions in lightning physics is the initiation of lightning. Studies have consistently shown that ambient fields in thunderstorms are too small to cause the dielectric breakdown of air. Two theories have emerged to explain this discrepancy: runaway breakdown and hydrometeor breakdown. In each theory, the ambient field is enhanced locally to the dielectric breakdown field. Early studies investigated the possible influence of various types of hydrometeors (i.e. supercooled water drops, ice crystals, graupel) on enhancing the ambient electric field and initiating breakdown. More recent studies have embraced runaway breakdown in which free electrons are accelerated by the ambient electric field. These electrons collide with atmospheric molecules, producing a number of slow electrons. This increases the conductivity in the atmosphere, producing enhanced electric fields. To date there has been no conclusive data that convincingly favors either the hydrometeor or runaway breakdown mechanism. In this presentation, a new study is introduced using multi-parameter radar and VHF lightning mapping array data. Hydrometeor environments are analyzed near lightning initiation centroids for several types of storms near Huntsville, AL, USA.
DE: 3304 Atmospheric electricity
DE: 3324 Lightning
SC: Atmospheric and Space Electricity [AE]
MN: 2007 Fall Meeting