Precipitation‐powered mechanisms of cloud electrification

Abstract

This article reviews those mechanisms of cloud electrification which are based on gravitational separation of precipitation particles and examines at some length the inductive charging mechanism. It is concluded that through the inductive mechanism, glaciated clouds can develop a maximum current density J max of 0.1 µA m −2 with a maximum field E max of about 3.5 × 10 5 V m −1 (which values are necessary for the occurrence of lightning flashes in them) within a time of 1000 s provided that the precipitation intensity in them is greater than 1.39 × 10 −5 m s −1 (50 mm hr −1 ). For precipitation intensities less than 8.33 × 10 −6 m s −1 (30 mm hr −1 ), J max and E max cannot develop to such high values. By its inherent nature this mechanism does not work in warm clouds.