Reduction of scavenging and increases in CCN concentration by electrical repulsion between droplets and particles: results from a Monte-Carlo simulation

The current flow in the global electric circuit deposits charge on both aerosol particles and droplets in gradients of conductivity in clouds, in accordance with Ohm's law and Gauss's Law. The conductivity gradients are caused by gradients in droplet concentration, both within and at the boundaries of clouds. Reductions in collision rate coefficients by an order of magnitude are found for charges of only 5e on particles and 50e on droplets, typical of modeled and measured charges in weakly charged layer clouds. Computed time constants for increases in CCN concentrations are of order a few hours. These results are relevant to aerosol processing in marine stratocumulus, especially where relatively highly changed residual aerosol particles from charged evaporating droplets are being generated.