Deposition (aerosol Physics) - Wet Deposition

In wet deposition, atmospheric hydrometeors (rain drops, snow etc) scavenge aerosol particles. This means that wet deposition is gravitational, Brownian and/or turbulent coagulation with water droplets. Different types of wet deposition include:

• Precipitation scavenging. This is where falling rain droplets collide with particles. This is also called "below-cloud scavenging".
• In-cloud scavenging. This is where aerosol particles collide with the water droplets in clouds. A common example of this type of deposition is inside fog. Clouds may also intercept with terrain (e.g. onto a mountain).
• Snow scavenging. This is where falling snow "removes" the material below it.
• Nucleation scavenging. This is where aerosol particles are activated to form cloud droplets and then are lost when the cloud droplets become rain drops. Within aerosol computer models aerosols and cloud droplets are mostly treated separately so that aerosol activation to cloud droplets represents a loss process that has to be parametrised