From the best published data, it is shown that to an approximation of ±4% the extinction coefficient for scattering by natural haze, when referred to its value at 0.61 µ varies as λ-0.7 in the region of wavelength from 0.61 to 11.48 µ regardless of the visual range. It is also shown that the relationship σ=kλ -0.7 for natural haze is consistent with the known range of sizes and indices of refraction of natural haze particles and their scattering area coefficients as given by the Mie theory. The possibility of this relationship holding also in ordinary smog is indicated.
MATHEW G. GIBBONS, "Wavelength Dependence of the Scattering Coefficient for Infrared Radiation in Natural Haze," J. Opt. Soc. Am. 48, 172-176 (1958)