Particle sizing of mixed-phase and cirrus clouds from phase function measurements

Abstract

A new method of particle sizing for mixed-phase and ice clouds proposed and tested by numerical simulation in authors' papers is applied here to experimentally measured scattering phase function. The method enables us to identify each component of a bi-component cloud composed of ice crystals and water droplets and to retrieve separately a size distribution for each cloud component. We use mainly available referenced data to test the inversion method with respect to the retrieval of size composition of mixed-phase and ice cloud under both single- and bi-component assumption and try to explain the known fact of the discrepancy between measured scattering phase functions for an ice cloud and those theoretically predicted by the ray tracing treatment, for instance, for convex ice crystals. Applying the inversion method enables us to show that one of effective ways to describe the scattering phase function behavior of mixed-phase and ice clouds is the bi-component assumption. It is rather natural for a mixed-phase cloud because of the existence of water droplets and ice crystals in the cloud simultaneously. On the other hand, one of an important physical reason for the bi-component assumption in an ice cloud lies in the well known fact that, as the cloud is transformed from water phase to ice one a high proportion of the particles can frequently stay as small supercooled water droplets even at very low temperature.