Lightning electromagnetic emission location using arrival time differencing ( LEELA ): An introduction to the Met Office's next generation Very Low Frequency lightning location system

Abstract

Abstract Lightning strikes occur in the atmosphere due to appreciable charge separation in cumulonimbus clouds. The detection of a lightning strike within such clouds is a vital indicator that other hazards such as severe rainfall, hail and aircraft effecting turbulence are also present, providing vital information for forecasters. The lightning discharge emits a broadband electromagnetic wave called a sferic which peaks in the very low frequency (VLF) range. Since the early 1900s the Met Office has operated some form of lightning location system that detects sferics at multiple receivers and can geolocate the position of the lightning strikes. This paper describes the operating principles of the Met Office's new VLF lightning location system: Lightning Electromagnetic Emission Location using Arrival time differencing (LEELA). Case studies comparing LEELA to ATDnet and other lightning location systems over the United Kingdom are shown. Using a set of 27 ground truths over the United Kingdom it is demonstrated that LEELA has 100% storm detection efficiency within 5 km of a ground truth and 93% detection efficiency within 2 km. LEELA has much improved detection capabilities, especially at night, with higher accuracy than its predecessor ATDnet, which had a 90% storm detection efficiency within 5 km of a ground truth.