Inferences about Ice Nucleation from Ice Crystal Observations

The total concentration of ice crystals found in natural cap clouds appears to result from the nucleating behavior of at least two types of ice nuclei, i.e., freezing and deposition. The respective contributions of these two modes of nucleation have been partitioned by the use of techniques in which the identification of ice crystals resulting from frozen droplets can be made. Furthermore, the identification of deposition ice crystals at water saturation, when compared with similar data obtained during water subsaturated but ice supersaturated conditions, has yielded an insight as to the dependence of deposition ice crystal concentration (deposition nuclei) upon both temperature and ice supersaturation.