Electrical and Microphysical Responses to Salt Seeding in Warm Maritime Cumulus Clouds

Abstract

Electrical, microphysical and dynamical responses to salt seeding have been investigated during cloud seeding experiments in several parts of India. Following massive salt seeding, increases in cloud temperature by I to 2 Celsius and cloud liquid water content up to 200 percent were observed in warm cumulus clouds (Ramahandra Murty eta., 1975, 1976). Cloud drop size distributions in seeded warm cumulus clouds increased in mean volume diameter up to 478 percent and computed liquid water content increased upward of 60 percent (Kapoor et al., 1976). In maritime warm cumulus clouds, which developed rain following seeding, the electric field reversed from initial negative to positive, occasionally preceded by intensification (Ramachandra Murty et al., 1976). This field reversal was attributed to the transport of large positive charges, from upper cloud levels to the base, by raindrops which form initially at higher levels in vigorous updraft regions. The prior intensification was attributed to updraft invigoration produced by massive salt seeding, since electrical activity is closely associated with convective activity (Latham and Stow, 1969).