Study of the Relationship between Ångström's Wavelength Exponent and Junge Particle Size Distribution Exponent

Abstract

The volume extinction coefficient produced by aerosol particles at wavelength λ is generally proportional to λ−α as found by Ånström. On the other hand, particle size spectra frequently give a particle number density approximately proportional to the inverse of the radius power with exponent ν, as found by Junge. On the basis of computations made using a very accurate Mie extinction algorithm, a study of the relationship curve between exponents α and ν is made for aerosol particle polydispersions of different radius intervals and for different refractive index values. Moreover, a set of relationship curves is obtained for realistic particulate extinction models based on different size distribution curves and refractive index models. The results show that the linear relationship α = ν − 2 is not valid in most cases. In particular, exponent α assumes appreciably lower values than ν − 2 in the range ν > 3 for all the particulate extinction models.