Model study on effect of hematite and goethite on optical properties of inhomogeneous desert dust aerosols

Desert dust aerosols occur as complex ensembles of particles with irregular shapes. Furthermore, these particles consist of a variety of different minerals which often coexist next to each other within individual particles. While in recent years the nonsphericity of particles is considered more and more in optical models of desert dust, the mineralogical inhomogeneity is still rarely considered though it can have a significant effect on light scattering and absorption.

Is this study, we discuss optical properties of irregularly-shaped inhomogeneous dust particles which were modelled with a Discrete Dipole Approximation code. We show how absorbing inclusions embedded in a non-absorbing material affect absorption and scattering by a particle as compared to the case when all the absorbing material is homogeneously distributed inside the particle. Hematite and goethite were selected as the material of the absorbing inclusions since these minerals are known to be responsible for most of the light absorption in desert dust aerosols.