Charge transfer during multiple large ice crystal interactions with a riming target

Laboratory studies of charge transfer between ice crystals and riming soft hailstones (graupel) have been extended using ice crystals of several hundred micrometers in diameter. The sign of the charge transfer is affected by cloud water content and temperature, being positive to soft hailstones at temperatures higher than about −18°C with typical values of cloud liquid water content. The d4 dependence of charge transfer on crystal size reported previously for smaller ice crystals decreases with larger crystals. The new data can be included in numerical models of thunderstorm electrification.