Improved technique for data inversion: optical sizing of multicomponent aerosols

Abstract

Estimation of particle-size distribution is analyzed for the complicated case of compound aerosols, in which particles are distinguished by sizes and optical constants. This task arises in a number of interesting practical situations when aerosol scatterers cannot be described with a common refractive index. This is an inverse problem with a large number of variables, and questions of formal inversion are of great importance here. They are discussed in detail, and an improved numerical-inversion method is proposed. The method provides a nonnegative and highly stable solution and makes it possible to include varied additional or a priori information. It is shown that the proposed technique is closely related to well-known linear and relaxation methods widely used in atmospheric optics. The algorithm for determination of bicomponent aerosol-size distribution is devised. It uses the intensity of light scattered at different angles and spectral-extinction measurements. In addition, the algorithm can incorporate a priori restrictions of size-spectra smoothness. A set of numerical examples illustrates the algorithm.