Clouds are important processors of atmospheric aerosol particles.
New particle mass can be formed by reactions of volatile species within cloud drops. For example, dissolved sulfur dioxide can be efficiently oxidized to sulfate in cloud drops. The sulfate is nonvolatile and remains as a particle residue when the cloud drop evaporates. Removal of aerosol particles can also be enhanced by clouds. Particles which are scavenged by cloud drops can be incorporated with the drops into precipitation which falls to the ground.