Abstract Current techniques for deriving cirrus optical depth and altitude from visible (0.65 μm) and infrared (11.5 μm) satellite data use radiative transfer calculations based on scattering phase functions of spherical water droplets. This study examines the impact of using phase functions for spherical droplets and hexagonal ice crystals to analyze radiances from cirrus. Adding-doubling radiative transfer calculations are used to compute radiances for different cloud thicknesses and heights over various backgrounds. These radiances are used to develop parameterizations of top-of-the-atmosphere visible reflectance and infrared emittance utilizing tables of reflectance as a function of cloud optical depth, viewing and illumination angles, and microphysics. This parameterization, which includes Rayleigh scattering, ozone absorption, variable cloud height, and an anisotropic surface reflectance, reproduces the computed top-of-the-atmosphere reflectances with an accuracy of ±6% for four microphysical models...