HR: 1330h
AN: AE32A-0157    [PDF]
TI: In Situ Observations of Lightning-Produced Nitric Oxide in Thunderstorm Cores
AU: * Helsdon, J H
EM: john.helsdon@sdsmt.edu
AF: Institute of Atmospheric Sciences, SD School of Mines and Technology 501 E. St. Joseph St., Rapid City, SD 57701-3995
AU: Detwiler, A G
EM: andrew.detwiler@sdsmt.edu
AF: Institute of Atmospheric Sciences, SD School of Mines and Technology 501 E. St. Joseph St., Rapid City, SD 57701-3995
AU: MacGorman, D R
EM: dmacgorm@gcn.ou.edu
AF: CIMMS/Univ. of Oklahoma, 100 E. Boyd Rm 1110, Norman, OK 73019
AU: Baker, B
EM: brad.baker@sdsmt.edu
AF: Institute of Atmospheric Sciences, SD School of Mines and Technology 501 E. St. Joseph St., Rapid City, SD 57701-3995
AU: Warner, T A
EM: tom.warner@sdsmt.edu
AF: Institute of Atmospheric Sciences, SD School of Mines and Technology 501 E. St. Joseph St., Rapid City, SD 57701-3995
AB: The SD School of Mines \& Technology armored T-28 aircraft was deployed to Norman, OK, from 14 May - 10 June 2003 in order to obtain measurements of lightning-produced nitric oxide (NO) mixing ratios in the cores of active thunderstorms (17 - 21 kft altitude range) in conjunction with lightning channel locations determined by the newly-installed NSSL lightning mapping array (LMA). To sample the NO, a TEI 42C-TL NO/NOx analyzer was used, operating in the NO-only mode. The inlet tube for the sampling system was situated above and behind the pilot's canopy along the aircraft axis. Six research and two calibration/test flights were conducted. Electric fields rarely exceeded 50 kV/m in the regions sampled with hydrometeors comprised of aggregates, graupel, and small hail. The TEI instrument often indicated broad regions of elevated NO that may have accumulated from many lightning discharges over a period of time, which were then distributed by convective circulations. A number of instances of narrow NO spikes were observed that we attribute to recent lightning discharges that passed through the sampled region. Peak values were typically from a few to 10s of ppbv. In one instance lightning attached to the T-28's propeller. The NO reading rose to ~180 ppbv in one second, then decayed. Depending on the actual time during which NO generated during this discharge entered the inlet (probably less than one second), and subject to a more refined calibration of the raw instrument reading, we estimate that the peak mixing ratio to have been in the range of 0.5-1 ppmv. With the LMA-derived lightning locations anticipated to be available shortly, we will present a more refined analysis of the overall NO mixing ratio structure within these thunderstorm cores as well as analyses of the NO spikes, focusing on the lightning strike to the aircraft.
DE: 0368 Troposphere--constituent transport and chemistry
DE: 3304 Atmospheric electricity
DE: 3324 Lightning
SC: Atmospheric and Space Electricity [AE]
MN: 2003 Fall Meeting