Estimations of charge transferred and energy released by lightning flashes

Abstract

Data from ground‐based and balloon‐borne electric field meters are used in conjunction with lightning mapping array data to estimate the amount of charge transferred and energy liberated by 40 lightning flashes in four New Mexico mountain thunderstorms. Two models are developed to estimate the lightning charge transfer: point charges at the geometric center of two or more lightning charge distributions, and uniform charge distributions placed along the lightning channels. Results indicate that flashes with substantial horizontal extent, primarily intracloud (IC) flashes during the storm's mature stage, are better modeled with uniform charge distributions. Less extensive flashes, both cloud‐to‐ground (CG) and early‐stage IC flashes, are better modeled with point charges. The amount of charge transferred by 29 IC flashes ranged from ±3.9 to ±85.8 C, with an average of ±17.6 C. Mature‐stage IC flashes transfer significantly more charge, on average, than early‐stage IC flashes. The 11 CG flashes transferred negative charge to the ground; the average amount of charge lowered was −8.7 C. All but one CG flash also had substantial in‐cloud charge transfers (average ±9.3 C, maximum ±44 C) in addition to the charge moved to the ground. Individual lightning charge transfers are combined with concurrent in‐cloud potentials to estimate the electrical energy released by each flash. The IC flashes released an average of 1.6 GJ of energy per flash, while the average for CG flashes was about half as much energy per flash. Using average charge and potential values for the group of storms yields lightning energy estimates of 2 × 108 to 7 × 109 J, depending on flash type and storm stage.