Dust Production by Density Currents - A Not So Well Known Source of Aerosol Particles in the Atmosphere

摘要

Dust is one of the most commonly found pollutants for many areas around the globe. Recent field and satellite observations suggest the importance of convectively generated downdrafts on the mobilization processes of dust particles and on their long range transport. RAMS/ICLAMS simulations of convective storms for the area of NW Africa allowed the description of the cool pool generation and the associated dust production mechanisms. Evaporation of rain droplets as they fall through the warmer and unsaturated air is responsible for the formation of a fast propagating density current. The inner structure of this system is characterized by increased turbulence, small scale vortices and strong updrafts at the edge of the front. Mobilization of dust occurs mainly in two ways: First, due to suspension of loose soil particles as the system passes over bare soil and sandy areas and second by sweeping pre-existing dust and creating a characteristic dust wall that reaches up to 3 km height.