Time and space correlation between sprites and lightning flash events for a storm case during HyMeX campaign
Abstract
During the SOP1 (Special Observation Period) of the HyMeX (Hydrology cycle in the Mediterranean eXperiment) campaign (September-November 2012), optical observations of sprite events were performed thanks to low light video cameras located in southern France. For the night of October 22nd - 23rd, a storm developed along the coastline in southeastern France, moved westward while producing a moderate lightning activity during about 4 hours, with a maximum cloud to ground (CG) flash rate of about 2 min-1 during the first half of its lifetime. The coldest cloud top temperature (-62°C) was simultaneous to this maximum flash rate. The horizontal extension of this storm (radar reflectivity larger than about 20 dBZ) reached around 200 km × 100 km during the second half, including a stratiform region and a little active convective region. Twelve sprite events were observed over this storm during this second half of the lifetime, while it was located in the area covered by a Lightning Mapping Array. The storm was located around a distance around 360 km and 230 km from camera 1 and camera 2, respectively. Each sprite event was associated with a positive CG stroke detected by the operational lightning detection networks, while the CG flash rate dramatically decreased. These positive strokes were detected below the stratiform region of the storm ahead of the convective system, and their peak currents range from 14 to 247 kA. The delay between the parent stroke and the sprite allows classifying the events within two categories, short delay (~ < 20 ms) and long delay (~ > 20 ms). Some of the sprite events were seen by two cameras and could be triangulated for a precise location. Observations of broadband ELF/VLF activity have been performed during this storm activity. They reveal a sustained VLF activity for cases of sprites with long duration and several elements shifted in time. On the contrary, the VHF activity is low during the sprite emission. The 3D location of the VHF sources allows describing leader paths and their correlation with the timing and the location of sprite elements. The location of the sprite elements coincide with the latest VHF activity before the sprite occurrence, characterized by scattered sources within the stratiform area generally remote from the primary VHF source of the flash sequence.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMAE33A0340S
- Keywords:
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- 0320 ATMOSPHERIC COMPOSITION AND STRUCTURE Cloud physics and chemistry