A three-dimensional mesoscale numerical model (Nickerson et al., 1986) with quasi-spectral microphysics has been extended to include gas and aerosol removal by cloud droplets and raindrops. Combining meteorological predictions and pollutant scavenging parameterizations, two-dimensional sensitivity tests have been carried out for continental and maritime clouds over an idealized topography. Nucleation scavenging is the most efficient in-cloud removal mechanism; however, differences in cloud droplet spectra between continental and maritime clouds lead to differences in their scavenging efficiencies for gases and aerosols, thereby emphasizing the need for the simultaneous treatment of meteorological and physicochemical processes. ¿American Geophysical Union 1987