Parameterization of size-dependent particle dry deposition velocities for global modeling

Dry deposition velocity of particles has been parameterized in the global multi-scale Chemistry and Transport Model MOCAGE as a function of particle size and density, surface properties, and micro-meteorological conditions near the surface. Hourly deposition velocities have been simulated over the year 2000 using the analyses and forecasts of the French operational numerical weather prediction model ARPEGE. Results were compared with measurements available in the literature. Predictions of our model are generally satisfactory, showing the largest uncertainty in the 0.1–1 μm particle size interval over highly rough surfaces. According to the one-year global average, deposition velocity over continents is about an order of magnitude higher than over oceans, for all particle sizes. Seasonal variations are nearly undetectable, while diurnal variations over land exist with a maximum around 12–15 h local solar time. Spatially, mid-latitudes regions usually have higher deposition velocities than tropical and polar ones, particularly over continents.