Capturing clouds

Abstract

Dust from the Sahara can directly drive the formation of cloud droplets over the eastern North Atlantic Ocean. Previously, dust was only known to trigger icecrystal nucleation or to produce liquid droplets after undergoing substantial atmospheric processing. Cynthia Twohy of Oregon State University and colleagues analysed the contents of clouds over the eastern North Atlantic Ocean. They found considerable quantities of dust particles in small clouds, with up to 80% of the sampled droplets containing dust. As dust naturally contains small amounts of material that can interact with water, these particles can be crucial in the formation of clouds, even near their source. The authors suggest that the infusion of Saharan dust into clouds could enhance albedo, decrease precipitation in shallow clouds and alter ice formation in deep clouds; these effects will be exacerbated if dust emissions increase as a result of changes in land use and climate.