Influence of complex component and particle polydispersity on radiative properties of soot aggregate in atmosphere

The Influence of Water Coating on the Optical Scattering Properties of Fractal Soot Aggregates

“…The results with the Maxwell-Garnett approximation agree quite well. Yin and Liu (2010) also used the MaxwellGarnett approximation and reported qualitatively similar results but did not consider error estimates. Here, with the inclusion of results with exact calculations using the CMGMM method, we are able to estimate and compare the relative errors introduced by each of the effective medium approximations.…”

“…Modeling the radiative impact of soot clusters in a manageable way in climate models is therefore an important matter. In humid atmospheric environments, soot aggregates frequently acquire a water coating, which introduces further complexity to the problem of determining the optical properties of the aggregates (Hanel 1976;Jones and Friedman 2000;Kocifaj et al 2008;Yin and Liu 2010). As described below, this study conceptually separates the geometric effects of aggregate structure from the effects of water coating and focuses on the latter.…”

“…As environmental relative humidity increases, the geometric size of an atmospheric aerosol increases significantly due to acquisition of a surface water coating (Hanel 1976;Jones and Friedman 2000;Kocifaj et al 2008;Yin and Liu 2010). Hanel (1976) studied the effect of relative humidity on atmospheric aerosol particles in moist air and found that small submicronsized particles may increase in volume by more than 25% when the relative humidity exceeds 70-80%.…”

“…Liu and Mishchenko (2005) showed that the increase in size of homogeneous monomers in aggregates, which results in increased overall aggregate size, has a major effect on the single-scattering properties, strengthening the forward scattering and weakening the backward scattering. More recently, Yin and Liu (2010) studied the scattering properties of aggregates composed of monomers coated by varying thicknesses of water, using the Maxwell-Garnett effective medium approximation to treat the monomers as homogeneous spheres. They found that the extinction, absorption, and scattering cross sections of the aggregates increased in the presence of the water coating.…”

“…Using these standards, the relative success of the two effective medium theories in approximating the effects of monomer water coating on the optical scattering properties is investigated. The MaxwellGarnet-based calculations of Yin and Liu (2010) are revisited and extended by both assessing the level of error involved in using that approximation, and by including analysis of results obtained using the Bruggeman approximation. First, water-coating effects for single monomers are examined, comparing each of the approximations with the exact results of core mantle theory.…”