A size-segregated particle dry deposition scheme for an atmospheric aerosol module

Abstract

A parameterization of particle dry deposition has been developed for the Canadian Aerosol Module (CAM).This parameterization calculates particle dry deposition velocities as a function of particle size and density as well as relevant meteorological variables. It includes deposition processes, such as, turbulent transfer, Brownian diffusion, impaction, interception, gravitational settling and particle rebound. Particle growth under humid conditions is also considered. Sensitivity tests show that the parameterization provides deposition velocities comparable with recent field observations, especially for sub-micron particles. The present parameterization has also been evaluated using two empirical bulk resistance models, which were originally developed from field observations. The present parameterization has been implemented in CAM, with meteorological input provided by the Canadian Regional Climate Model (RCM) to the eastern North America. A comparison of the modelled dry deposition velocities to a variety of recent measurements that have been reported in the literature demonstrated that the current parameterization produces reasonable results. The main improvement of the current parameterization compared to earlier size-dependent particle dry deposition models is that the current one produces more realistic deposition velocities for sub-micron particles and agrees better with recently published field measurements.