RAINDROP CHARGE AND ELECTRIC FIELD IN ACTIVE THUNDERSTORMS

Abstract

The electrical characteristics of two active spring thunderstorms are reported. Simultaneous surface measurements of the sign and magnitude of the free charge on individual raindrops, the electric field and precipitation rate have been made. More than 7000 drops, representing a continuous sample of the drops falling in the storms, show no important systematic dependence on the sign or magnitude of the instantaneous electric field. The measurements show that the convected current to the earth frequently exceeds the conduction currents by a large factor, and, therefore, the charged rain may determine the electric field at the surface. The average measured free charge brought down by positively charged rain was 0.022 esu per drop, and by negatively charged rain was 0.031 esu per drop. The ratio of the negative free charge to the positive free charge brought down by rain was 1.2, while the ratio of the number of negative drops to the number of positive drops was 0.88.