Extinction by Aerosol Clouds of Nonspherical Particles at Arbitrary Wavelengths

Extinction by a cloud consisting of many aerosol particles has been found to fall into two distinct wavelength regions which are adequately described by the geometric optics theory and the Rayleigh theory. Because the cloud consists of many different particles, the narrow extinction resonance structure of individual particles is lost, and extinction is governed by shape and size as predicted by geometric optics. At longer wavelengths, particles are in the Rayleigh region, and extinction for a large variety of particle shapes is predicted by the Rayleigh ellipsoidal theory. The transition region lying between the applicability of these two simple theories occupies only about one wavelength decade.