Modified gamma distribution was used to describe the distribution of particles in clouds. The polydisperse particle
system may be converted into a monodisperse particle system. 1) The averaged radius of nonspherical particles
associated with a given size distribution, 2) the averaged scattering parameters of water droplets in cumulus, stratus and
stratocumulus and that of ice crystals in cirrus, and 3) infrared emissivity of a cirrus layer from the mixing ratios and
effective sizes of cloud drop and ice crystal were separately calculated. Simulation results indicate that all scattering
parameters of water droplets in cumulus, stratus and stratocumulus are similar. Cross sections increase with the
increasing equivalent radius. While efficiency factors vibrate with the increase of equivalent radius. The averaged albedo
reaches its peak between 2 and 3 micron, and then decrease with the increasing equivalent radius. The averaged
asymmetry factor also vibrates with the increase of equivalent radius. But the scattering parameters of ice crystals in
cirrus change differently, and they vary linearly with equivalent radius.
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