Effective refractive indices of water and sulfate drops containing absorbing inclusions

In this study the range of visible refractive indices and single-scattering albedos that can be obtained using various mean field formulations for mixtures of two components, where one component absorbs in the visible, is explored. For calculations of global radiative forcing and climate response, such formulations provide a convenient way to take into account internal mixing of aerosol components without the computational burden of a more exact theory, provided that the limits of their applicability are kept in mind. Within those limits, the results show that for water and sulfate drops containing dust and soot inclusions, the degree of interaction between the electric fields of neighboring inclusions is not important. However, the shape and size of the inclusions can cause a variation in the effective imaginary refractive index of up to a factor of 3.4 and a variation in the single-scattering albedo of up to 0.18 in absolute value.