A DNS study of aerosol and small-scale cloud turbulence interaction

The purpose of this study is to investigate the interaction between small-scale turbulence and aerosol and cloud microphysical properties using direct numerical simulations (DNS). We consider the domain located at the height of about 2000 m from the sea level, experiencing transient high supersaturation due to atmospheric fluctuations of temperature and humidity. To study the effect of total number of particles (N_tot) on air temperature, activation and supersaturation, we vary N_tot. To investigate the effect of aerosol dynamics on small-scale turbulence and vertical air motion, we vary the intensity of turbulent fluctuations and the buoyant force. We find that even a small number of aerosol particles (55.5 cm^-3), and therefore a small droplet number concentration, strongly affects the air temperature due to release of latent heat. The system comes to an equilibrium faster and the relative number of activated particles appears to be smaller for larger N_tot. We conclude that aerosol particles strongly affect the air motion. In a case of updraught coursed by buoyant force, the presence of aerosol particles results in acceleration of air motion in vertical direction and increase of turbulent fluctuations.