Effects of aggregation on scattering and radiative properties of soot aerosols

The superposition T‐matrix method is used to compute the scattering matrix elements and optical cross sections for a wide variety of fractal‐like soot aggregates in random orientation at a visible wavelength 0.628 μm. The effects of the fractal dimension and prefactor, the monomer radius, the number of monomers in the aggregate, and the refractive index on light scattering and absorption by aggregated soot particles are analyzed. It is shown that the configuration of the monomers can have a substantial effect and that aggregation can result in a significant enhancement of extinction and scattering relative to those computed from the Lorenz–Mie theory, assuming that there are no electromagnetic interactions between the monomers. Thus one must take the effects of soot agglomeration and cluster morphology into account in radiative transfer modeling and remote sensing applications.