Airborne studies of thunderstorm electrification

Abstract

THERE is considerable controversy^1,2 surrounding the problem of thunderstorm electrification. Many scientists have maintained that precipitation acquires substantial charges and that field growth to breakdown magnitudes is a consequence of the separation under gravity of the precipitation and the oppositely charged cloud particles. Others have argued that precipitation is incidental to field growth, and have reported lightning from clouds in which the precipitation rates are very low. Of the charging mechanisms involving precipitation, the inductive mechanism^3,4 has been generally favoured. Under this mechanism rebounding collisions of small cloud particles with the underside of precipitation elements result in the removal from the latter of polarisation charge, and the maximum charge Q_m (pC) that can be acquired by an element of diameter d (mm) in a field E (kV cm ⁻¹) is given by Q_m = 5.5Ed² (1)