Spatial and temporal evolution of horizontally extensive lightning discharges associated with sprite‐producing positive cloud‐to‐ground flashes in northeastern Spain

Abstract

During the evening of 6 August 2008, a small mesoscale convective system (MCS) entered the area of radar and 2‐D interferometric lightning detection system coverage in northeastern Spain and produced 17 sprites recorded by a camera at only 95–180 km distance. This study presents an analysis of the in‐cloud component of the sprite‐associated lightning flashes and those of other flashes. The analysis focuses on the horizontal development of sprite‐producing lightning by discussing three examples, divided into the periods before the positive cloud‐to‐ground flash (+CG), between +CG and the end of the sprite, and the period after the sprite. Location and horizontal size of sprites appear to be well explained by the temporal and spatial development of the lightning path. The majority of sprite‐producing discharges started directly at the rear side of developing and mature convective cores within the decaying MCS, either with the +CG or with preceding negative leaders. The +CG started a burst of VHF sources during which the sprite developed. Delayed carrot sprites developed after a secondary, smaller burst and were well collocated with the burst toward the rear of the MCS. The order of development of elements in a grouped sprite followed the direction of lightning propagation during the burst stage. The second part of the analysis concentrates on the metrics of sequences of VHF sources and shows that sprites are indeed produced by the largest, longest lasting discharges with particularly large line‐perpendicular dimensions (37 km median compared with 11 km for +CG >25 kA).