PHASE STRUCTURE OF CLOUDS

I. P. Mazin

Extensive experimental data on cloud phase structure collected at a special network of aircraft stations in the former Soviet Union in 1957—1963 and the data obtained within Canadian cloud projects in the 1990s are analyzed and compared. A necessity to distinguish between the cloud phase structure for the whole cloud and for a local cloud parcel (volume) is emphasized. The local cloud phase structure (LCPS) depends on the scale of averaging. The main parameter that determines the frequency of occurrences of different LCPS (for a given scale of averaging) is temperature. The average LCPS characteristics for different cloud types are different, while geographical or time of year variations are of secondary importance. A parametrization is proposed that describes the dependence on temperature of the local cloud phase index that characterizes the ice fraction of the cloud water. We also discuss problems related to the averaging of empirical data on cloud phase structure. Problems the experimental cloud physics faces when cloud phase structure is investigated are formulated.