A parameterization of the single scattering properties of an aerosol for a dust layer in the solar spectral region is presented. The parameterization scheme accounts for the microphysical changes of an aerosol layer and is applied to dust and waterclouds. A scaling parameter is presented which describes, simply and effectively, the optical properties of an aerosol layer with a large effective size parameter. ¿ American Geophysical Union 1988