The asymmetry factor (g) describes the amount of forward or backward scattering by an aerosol particle, and is primarily a function of particle size distribution. The asymmetry factor (g) is a measure of the directionality of scattering, defined as:
and ranges from -1 to +1. For symmetric scattering (Rayleigh scattering), g = 0. Forward scattering is indicated by g = +1 and for backward scattering, g =— 1. For the UV wavelength region, g typically falls in the range 0.6 to 0.8 (Madronich, 1993). Lacis and Mishchenko (1995) present slight differences in g for aerosols of differing chemical composition. Soot and large desert aerosols generally have g ~ 0.9, and for sulfate, marine, and smaller dust aerosols, g ranges from 0.65 to 0.8.
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