HR: 0800h
AN: AE31B-0169    [Abstracts]
TI: Cloud-to-ground and Intracloud lightning activity associated with Sprite events observed over France on 23 July 2003
AU: Knutsson, L
EM: knutsson_lars@hotmail.com
AF: Laboratoire d'Aerologie, UMR 5560 UPS/CNRS, 14 av. E. Belin, Toulouse, 31400 France
AU: * Soula, S
EM: sous@aero.obs-mip.fr
AF: Laboratoire d'Aerologie, UMR 5560 UPS/CNRS, 14 av. E. Belin, Toulouse, 31400 France
AU: Van der Velde, O
EM: vdvo@aero.obs-mip.fr
AF: Laboratoire d'Aerologie, UMR 5560 UPS/CNRS, 14 av. E. Belin, Toulouse, 31400 France
AU: Neubert, T
EM: neubert@dsri.dk
AF: Danish Space Research Institute, Juliane Maries Vej 30, Copenhagen, 2100 Denmark
AU: Rasmussen, i
EM: iblr@dsri.dk
AF: Danish Space Research Institute, Juliane Maries Vej 30, Copenhagen, 2100 Denmark
AU: Allin, T
EM: tha@oersted.dtu.dk
AF: Danish Technical University, Bygn.327, Lingby, 2800 Denmark
AB: As a part of the European research program CAL, sprite observations were carried out from the Pic du Midi observatory in the French Pyr‚n‚es during the summer 2003. Images of the sprites were taken by two remotely controlled CCD cameras. The 23 July observations are considered particularly interesting because we then had access to data concerning both cloud-to-ground and intracloud lightning activity. A large thunderstorm with two convective cores, one to the north and the other to the south, developed over the South of France during the late afternoon, and about two hours after sunset, the first sprite was detected. During a little more than three hours, 13 sprites were observed, 7 over the northern system and 6 over the southern system. The images enabled us to determine the azimuth angle of each sprite from the OMP observatory. 12 of the 13 sprites could be associated to positive cloud-to-ground flashes, and one could be associated with intracloud flash. Satellite images were included at this point of the study, and it appeared clear that sprites tend to occur over the stratiform region of the storm system in the area with the coldest (highest) cloud tops. The associated positive flashes were also within or close to this portion of the storm. The sprite occurrences are studied in relation to the cloud-to-ground and to the intracloud activity. We find that sprites seem to occur in a late stage of each storm system, when the rate of negative cloud-to-ground flashes has considerably decreased, and when the ratio of positive cloud-to-ground flashes is much higher than during the most active phase of the storm. Globally, the intracloud activity is also low during the sprite-producing periods, but sudden "bursts" of intracloud lightning could frequently be observed at the moment of the sprite. The area coverage of the radar echo was calculated. The result supports the idea that sprite events tend to appear almost exclusively over large thunderstorm systems.
DE: 3304 Atmospheric electricity
SC: Atmospheric and Space Electricity [AE]
MN: 2004 AGU Fall Meeting