Electrification accompanying the melting of ice particles

It was observed that during the melting of small ice particles supported in a vertical wind tunnel, strong convection currents developed in the melt water. Bubbles released from the ice during melting were swept up by the currents and rapidly transferred to the surface where they burst. The separation of electric charge accompanying the bursting of the bubbles was highly dependent on the convection currents in the water. The observed charging effects are not entirely consistent with theories based on the disruption of an electric double layer. In particular, the separation of charge is considerably increased if the air contains high concentrations of CO2. It is shown that the observed values of charge separation are sufficient to account completely for the presence of the lower pocket of positive charge found below the melting level in many thunderstorms.