Volumetric scattering and absorption by aerosols: parametric sensitivity in Mie modeling and comparisons to observations

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Abstract
Aerosol complex indices for soot, ammonium sulfate, methylene blue, ambient, Arizona road dust, and combinations were employed in Mie calculations to determine the volume scattering and absorption coefficients βs and βa, respectively. Parametric aerosol properties (i.e., number density, particle size distribution, optical complex index of refraction, and particle shapes) were used in the first principles of Mie calculations to derive βs and βa, which were then compared to corresponding measurements. The result of the βs and βa calculation was found to depend very sensitively on the number density and size distribution of the aerosols and less strongly on the optical complex index of refraction. The refractive and absorptive portions of the index affect the wavelength dependence of βs and βa. When particles are of irregular shapes or when they agglomerate, the effect is to produce increased scattering, the amount depending on the sizes and numbers of the asperities or constituents of the agglomerates.