HR: 0800h
AN: AE31A-0153    [Abstracts]
TI: Statistical Characterizations of TLEs and Their Parent Lightning Discharges
AU: * Lyons, W A
EM: walyons@fma-research.com
AF: FMA Research, Inc., Yucca Ridge Field Station 46050 Weld CR 13, Fort Collins, CO 80524 United States
AU: Nelson, T E
EM: tnelson@frii.com
AF: FMA Research, Inc., Yucca Ridge Field Station 46050 Weld CR 13, Fort Collins, CO 80524 United States
AU: Andersen, L
EM: ande3164@blue.unco.edu
AF: FMA Research, Inc., Yucca Ridge Field Station 46050 Weld CR 13, Fort Collins, CO 80524 United States
AU: Cummer, S A
EM: cummer@ee.duke.edu
AF: Duke University, Dept. of Electrrical and Computer Engineering, Durham, NC 27708 United States
AU: Huffines, G H
EM: Gary.Huffines@unco.edu
AF: University of Northern Colorado, Dept. of Earth Sciences, Greeley, CO 80639 United States
AU: Rodger, C J
EM: crodger@physics.otago.ac.nz
AF: University of Otago, Dept. of Physics, Dunedin, Box 56 New Zealand
AB: The characteristics of sprites, halos and elves (collectively termed Transient Luminous Events [TLEs]) and their parent lightning discharges have been documented for individual storms (Lyons 1996; Lyons et al. 2000; 2004). Several summer observation campaigns conducted at the Yucca Ridge Field Station (YRFS), notably the Severe Thunderstorm Electrification and Precipitation Study (STEPS) of 2000 (Lang et al. 2004), have allowed the determination and analysis of the characteristics of a large number (>1000) of TLEs and their parent CG strokes. The optical characteristics of the TLEs are now being linked to various relevant parameters including NLDN polarity and peak currents, charge moment changes (CMCs) determined from ELV/VLF signatures. (Cummer and Lyons 2004), LMA-determined altitudes and areas of charge removal, and storm morphological characteristics (cloud heights, areal coverage, reflectivity, age, etc.) The assembly of this large database is an ongoing process that will take another year for completion. However, some preliminary results will be presented. The geographical distribution of TLEs optically detected from YRFS will be mapped. The distribution of sprite parent +CGs shows a broad range of peak currents from 9 kA to 237 kA (mean of 58 kA) while TLEs with halos and/or elves ranged from 11 kA to 266 kA (mean of 112 kA). This is consistent with previous studies indicating peak currents for halos/elves are roughly twice that for sprites, and both are significantly larger than the average +CG value in the storm. However, given its variability, peak current is not a good predictor of TLE potential. Various approaches to computing CG charge moment changes are showing a clear separation in distributions between TLE and non-TLE producing +CGs. Statistics on time of occurrence, sprite morphological relationships to CMCs, and sprite onset time delays will also be presented. Given the temporal imprecision of video, the TLE onset delay after the return stroke can only be estimated. Approximately one third of TLEs onset within the first 17 ms, though almost 20% delay for 60 ms or longer. No High Plains sprites associated with negative CGs have been confirmed, though there are some negative CG halo candidates. No blue jets have been monitored from the ground at YRFS in a decade. Is this due to (1) difficulties in monitoring a blue signature through >100 km of atmosphere, and/or or (2) the rarity of this phenomenon over the U.S. High Plains? The unexpectedly high frequency of large peak current (>200 kA) negative (but not positive) CGs detected by the NLDN over tropical oceanic regions, an environment in which giant blue jets have been observed, has lead to questions as to whether such large peak currents are real or an artifact (Lyons et al. 1998). A climatology of large peak current CGs for the New Zealand Lightning Detection Network found some evidence of enhanced large peak current -CGs over surrounding oceanic regions. The pattern, however, is complicated by apparent enhancements in high peak current CGs of both polarities in mountainous regions, an affect not documented by the U.S. NLDN.
DE: 3324 Lightning
DE: 3314 Convective processes
DE: 0342 Middle atmosphere--energy deposition
SC: Atmospheric and Space Electricity [AE]
MN: 2004 AGU Fall Meeting