Assessment of cloud optical parameters in the solar region: Retrievals from airborne measurements of scattering phase functions

Abstract

A data set of approximately 60,000 airborne measurements of angular scattering coefficients was used to reproduce a representative set of both microphysical parameters and single light-scattering characteristics (angular scattering coefficient, asymmetry parameter, single-scattering albedo, and extinction coefficient) for three types of clouds. The measurements were limited to a wavelength of 0.8 μm and to 28 scattering angles near uniformly positioned from 15° to 155°. Microphysical and optical characteristics were computed at wavelengths of 0.8, 1.6, and 3.7 μm, which are needed for the direct and inverse modeling of radiative transfer. The estimation of these characteristics is achieved through cloud microphysical parameter retrievals, taking into account the variation of water droplet and ice crystal size as well as cloud phase composition. We present both average values and possible variability of microphysical and single-scattering characteristics for three types of clouds with respect to their particle phase composition (i.e., water droplets, mixed phase, and ice crystals in cloud). The variations are presented separately due to both random instrumental errors of optical measurements and possible changes in the microphysical parameters within a separated specific cloud category. The microphysical parameter retrievals are validated by comparison with collocated direct particle size distribution measurements. Additionally, the estimated single light-scattering characteristics are in reasonable agreement with those available from the literature. © 2003 by the American Geophysical Union.