Inference of cirrus cloud properties using satellite-observed visible and infrared radiances. Part II: verification of theoretical cirrus radiative properties

Abstract

A methodology is developed to apply a parameterization of radiative transfer calculations to satellite analyses of cirrus clouds. Cloud heights and optical depths are derived from visible and infrared window measurements taken during the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment (FIRE) when cirrus clouds were present. Geostationary satellite retrievals are compared to lidar-derived cloud heights and retrievals from a polar-orbiting satellite taken at different angles to determine which theoretical models of scattering phase function and single-scattering albedo best represent actual cirrus clouds. Models using small hexagonal ice crystals with a diameter of 20 μm (C20) and a size distribution of slightly larger hexagonal ice crystals representing a cirrostratus (CS) cloud produce the best results. Interpretation of cirrus reflectance with water-droplet models leads to biased results. This finding has important implications for the cirrus cloud properties derived by the ISCCP. The cloud-height and optical depth biases can be minimized with the use of the C20 or CS models. -from Authors