A relationship between liquid water content and chemical composition in clouds

In this paper we present two-year results from the Cloud Chemistry Measurements Programme, carried out at Mt. Brocken/Hart (Germany) to assess the influence of cloud physical parameters on the chemical composition of clouds. There are large variations in the chemical composition of cloud water. We found that the liquid water content of clouds predominantly determines the ionic content. The relationship is best approximated by a power function, nearly identical for all chemical species. We identified deviations of data points from the general relationship accompanying events with different air pollution situations. An important conclusion is that cloud chemistry monitoring in the sense of air pollution studies is meaningless without measurement of cloud physical parameters. These are liquid water content, cloud base altitudes, and to some extent, droplet size distribution.