Tuesday, 22 January 2008: 4:00 PM
Meteorological Origin of Q-bursts and Sprites over West Africa
222 (Ernest N. Morial Convention Center)
It is increasingly well established on the basis of a growing number of Schumann resonance (ELF) observations that Africa is the predominant source (among three tropical ‘chimney' regions) of giant positive ground flashes, resonance-ringing Q-bursts, and mesospheric sprites. The presumed explanation for this dominance is the highly baroclinic nature of the atmosphere between rainforest and desert in West Africa that supports an abundance of westward moving squall lines (mesoscale convective systems) with trailing stratiform regions. This study makes use of the MIT Doppler radar, local electrical measurements, and remote ELF measurements at multiple sites (Japan, Hungary, Israel, USA) to document the meteorological origin and context of these exceptional lightning flashes in Niamey, Niger. Consistent sequences of lightning behavior are observed from leading deep convection through the transition region to the trailing stratiform precipitation, and will be compared with vertical radar cross-sections through squall line structure. The onset of prominent “bell-ringing” lightning (some with durations of 2-3 seconds) requires the presence of the radar bright band. Comparisons between the depth, structure and lateral extent of the stratiform regions and the magnitude of the lightning produced (based on remotely sensed ELF radiation) will be discussed.