Incorporating Particle Settling Enhancement in a Coarse‐Mode Deposition Model

Abstract Dry deposition rates are usually assumed to rely primarily on gravitational settling, with some enhancement due to interactions with surface elements. However, it is known through experiment, theory, and simulation that vertical velocities of particles in turbulent flows can be enhanced by hydrodynamic effects (often referred to as preferential sweeping), which is not explicitly captured by current deposition models. In this work, we leverage scaling analysis of the atmospheric surface layer to develop a coarse mode deposition model that incorporates preferential sweeping. We find that scaling laboratory experiments to field scales points to an increase in the settling velocities of coarse‐mode particles at all heights, though the expected increase is less than limited empirical observations might suggest. We emphasize the likely reasons for this discrepancy and highlight that more research focus should be placed on appropriately modeling the deposition rate of such particle sizes due to these uncertainties.