Pollution and Clouds over the Massif Central

Abstract

Clouds play an important role in our environment. Apart from their radiative properties, this is due to the fact that they capture, transport and modify atmospheric pollutants. To understand their role in our climate is a long-standing aim. Concerning the pure liquid clouds the work has already considerably advanced, as there exist numerous models that study, e. g., the fate of sulfur, ozone or aerosol scavenged by clouds (e. g. Hall, 1980; Chaumerliac et al., 1987 a, b; Flossmann et al., 1988; Flossmann, 1991). For temperature regions from −0°C to −20°C, however, ice particles coexist with liquid water drops in the clouds and, thus, interfere in the processing of pollutants. Concerning these so-called mixed phase clouds our understanding is less advanced. There exist few model approaches which, however, lack from the fact that little is known on the fate of scavenged material in drops once the drops freeze. In order to shed light on this problem the European project CIME (Cloud Ice Mountain Experiment) has been initiated to study this problem. To support this experiment, dynamical microphysical and chemical models have been prepared which will in a later phase be used to interpret and generalize the findings.