Large Ice Crystal Charge Transfer Studies
Final rept. Sep 87-May 91,
UNIVERSITY OF MANCHESTER INST OF SCIENCE AND TECHNOLOGY (UNITED KINGDOM) DEPT OF PHYSICS
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Studies of charge transfer between ice crystals and a graupel pellet have been made in a laboratory cold room. The dependence of charge transfer upon liquid water in the cloud has been quantified and together with previously determined dependencies on crystal size and velocity, relationships have been found between the parameters that control the charge sign and magnitude. These results may be used in numerical models of the electrification of thunderclouds. The charge transfer mechanism is discussed in terms of two competing mechanisms leading to positive and negative pellet charging. The validity of the experimental techniques used has been verified by studying the charge to ice spheres freely falling through an ice crystal and supercooled droplet cloud. Other work has involved the collision efficiency of graupel pellets for ice crystals, the heat transfer coefficient of riming graupel pellets, and the scavenging of aerosol particles.