Aerosol Models

Airborne aerosol particles consist of fragments of solid particulate matter (PM) mixed with solute substances for humid air conditions. This chapter provides a picture of the main shape parameters of the number density size-distribution curves characterizing the aerosol types most frequently observed in the atmosphere and describes the most relevant optical characteristics of aerosols. A number of aerosol extinction models of different origins are described to characterize their scattering and absorption properties. Within the atmospheric layers where aerosols contain significant mass fractions of soot and other organic substances, a relevant percentage of incoming solar radiation is absorbed, leading to an appreciable warming of such atmospheric layers. Detailed descriptions of the microphysical and optical characteristics of the 43 aerosol extinction models are also presented. The sets of optical data calculated for 43 aerosol extinction models can be conveniently used to evaluate the scattering and absorption effects produced by the various aerosol types.