HR: 11:16h
AN: AE12A-04    [Abstracts]
TI: Statistical Studies of Ground-Based Optical Lightning Signatures
AU: Hunt, C R
EM: crhunt@mit.edu
AF: ISR-4, Los Alamos National Laboratory, MS-D448, Los Alamos, NM 87545 United States
AU: * Nemzek, R J
EM: nemzek@lanl.gov
AF: ISR-4, Los Alamos National Laboratory, MS-D448, Los Alamos, NM 87545 United States
AU: Suszcynsky, D M
EM: dsuszcynsky@lanl.gov
AF: ISR-2, Los Alamos National Laboratory, MS-D448, Los Alamos, NM 87545 United States
AB: Most extensive optical studies of lightning have been conducted from orbit, and the statistics of events collected from earth are relatively poorly documented. The time signatures of optical power measured in the presence of clouds are inevitably affected by scattering,which can distort the signatures by extending and delaying the amplitude profile in time. We have deployed two all-sky photodiode detectors, one in New Mexico and one in Oklahoma, which are gathering data alongside electric field change monitors as part of the LANL EDOTX Great Plains Array. Preliminary results show that the photodiode is sensitive to approximately 50% or more of RF events detected at ranges of up to 30 km, and still has some sensitivity at ranges in excess of 60 km (distances determined by the EDOTX field-change array). The shapes of events within this range were assessed, with focus on rise time, width, peak power, and their correlation to corresponding electric field signatures, and these are being compared with published on-orbit and ground-based data. Initial findings suggest a mean characteristic width (ratio of total detected optical energy to peak power) of 291 +/- 12 microseconds and a mean delay between the RF signal peak and optical peak of 121 +/- 17 microseconds. These values fall between prior ground-based measurements of direct return stroke emissions, and scattering-dominated on-orbit measurements. This work will promote better understanding of the correspondence between radio and optical measurements of lightning.
DE: 0321 Cloud/radiation interaction
DE: 3304 Atmospheric electricity
DE: 3324 Lightning
DE: 3394 Instruments and techniques
SC: Atmospheric and Space Electricity [AE]
MN: Fall Meeting 2005