Hygroscopic seeding effects of giant aerosol particles simulated by the Lagrangian-particle-based direct numerical simulation

This study investigated the microphysical responses to seeding giant aerosol particles and supersaturation fluctuations. A Lagrangian-particle-based direct numerical simulation is used to resolve the interactions among individual aerosols, droplets, and the fluctuating supersaturation field within a turbulent, adiabatic air parcel. It is shown that the giant seeding particles exert strong solute effects throughout the entire simulation to alter the subsequent collision–coalescence process, implying the importance of including the solute term in droplet growth. Small-scale supersaturation fluctuations in adiabatic cloud regions have a negligible influence on aerosol activation and droplet condensation. This is because in regions free of entrainment and/or large-scale mixing, the weak supersaturation fluctuations can be quickly smoothed out via diffusion and remain relatively small in magnitude (with a standard deviation <urn:x-wiley:00948276:media:grl63176:grl63176-math-0001). In contrast, the activation in our simulations is determined by the seeding modulation of the parcel-mean supersaturation.