Dependence of Neutralized Charge Amount on Meteorological Conditions in Summertime Lightning Discharges in Japan

Abstract

Lightning discharges in Gunma Prefecture, Japan, from June–September 2023 were analyzed to explore the dependence of the neutralized charge amount on cloud structures embedded in weather systems, mainly based on in situ measurements of the ground‐based electric field, radar and satellite remote sensing, and numerical simulations using a bulk lightning model. Two types of lightning episodes distinguished by meteorological conditions were identified during the analysis period: lightning discharges in frontal cloud systems with abundant hydrometeors and lightning discharges in isolated convective storms under highly unstable conditions. Lightning discharges in frontal cloud systems were characterized by a large amount of neutralized charge and high lightning frequency. This was attributed to abundant graupel between the −10°C and −20°C levels, a critical temperature range for charge separation. In contrast, the neutralized charge amount was approximately three times smaller in isolated convective storms. In this case, graupel was mainly distributed above the −20°C level, outside the critical temperature range, resulting in a reduced amount of charge carried by hydrometeors.