Two points are addressed: (1) As has been noted, the method most commonly used to assess the contribution of a single, charged precipitation particle to the rate of change of electrostatic energy of a thunderstorm is problematic. Equating the rate to the product of the net electrical force and a velocity leads to an arbitrary value of the contribution of a single particle. Here this arbitrariness is removed by viewing the contribution of a single particle as being due to its motions with respect to all the other individual charges. It is also shown that in spite of this arbitrariness of the usual method when applied to individual particles, it nonetheless yields a nonarbitrary value for the total rate of change of electrostatic energy for the whole collection of charges. (2) In the event that differences in sedimentation velocity are not adequate to account for the electrification of thunderstorms, this does not imply that all precipitation-based mechanisms are ineffective, as is sometimes suggested. The possibility yet remains that convective processes may be effective in driving the large-scale separation of precipitation particles from other charged particles. ¿American Geophysical Union 1987 |