A numerical model was constructed to simulate the scavenging of hygroscopic aerosols with the aim of studying the influence of several meteorological parameters on the composition of rainwater and the atmospheric aerosol content. The scavenging mechanism is found to be highly dependent on (1) the relative humidity RH, especially in relation to its effect on the size distribution of hygroscopic particles (for non-hygroscopic particles the concentration effect during scavenging for low relative humidity is not so pronounced because the scavenging coefficients decrease as the impurities in the raindrops are being concentrated due to evaporation; e.g., for a rainfall intensity of 1.2 mm/h, 0.5-mm rainfall, and nonhygroscopic particles, the average rainwater concentration for RH=50% is only 1.2 times larger than that for RH=94%), (2) the rainfall intensity (or more fundamentally the raindrop size spectra), especially for small rainfalls, and (3) the chemical nature of the particles. With the assumption of no particle replenishment, only 20% of the initial aerosol mass remained in the subcloud layer after 4-mm rainfall for the best scavenging conditions and after 15-mm rainfall for the worst conditions. Therefore after these rainfalls, changes in the rainfall intensity and relative humidity would have little effect on the average rainwater concentration, since little aerosol mass remains to be scavenged. The model predictions of average rainwater concentration variations due to meteorological parameter changes are consistent with values actually measured.