Spatio-Temporal Distributions of Lightning Stroke Charge Using ELF and Meteorological Data

Abstract

AbstractIn this paper lightning stroke charges are estimated remotely by using combinations of Extremely Low Frequency (ELF) radio waves, conventional Lightning Locating System (LLS) and local meteorological information for the first time. Each lightning stroke location from LLS and corresponding transient signature of ELF magnetic field observed at a long distance (−1000 km between lightning stroke and observation site) are utilized to estimate the charge moment change (CMC) of the lightning stroke. The lightning stroke charge Q is then derived by dividing the CMC by the altitude of the neutralized lightning charge. The corresponding altitude of the neutralized lightning charge for each stroke is determined by assuming local −20 °C altitude for a positive stroke (−10 °C altitude for a negative strokes) from MesoScale Model (MSM). Spatial and temporal frequency distributions of energetic lightning (large amount of stroke charge) and cumulative frequency distributions of stroke charge in northwestern part of Japan in local summer and winter seasons for 4 years were derived. The spatial occurrence frequency distributions indicate that lightning strokes with a large amount of neutralized charge occur more frequently in inland areas during summertime and in coastal areas in winter. The cumulative frequency distribution indicates that positive polarity lightning strokes in winter tend to have a large charge. Our statistical results are in good agreement with the lightning properties inferred from local observations, and are considered to be useful information not only to study electrical properties of thunderstorms but also for future maintenance planning of power grid systems in wide areas and mitigation of lightning damages.KeywordsLightning chargeELFCharge moment change