Comprehensive Characterization of Size-resolved Composition and Morphology of Mineral Dust Particles for Radiative Forcing Studies

Improved understanding of the properties of mineral aerosols is needed for both the interpretation of atmospheric radiation observations and for radiative forcing modeling. Complex shapes and source-dependent heterogeneous composition of mineral particles pose the main challenge in developing the reliable treatments of dust. We present the results of a comprehensive analysis of a unique data set of physicochemical properties of mineral dust representative of active dust production regions in the Sahel and China. Mineral dust aerosols were generated from natural soil samples in the laboratory wind-tunnel experiment in a way similar to saltation and sandblasting processes that are responsible for mineral dust emissions in natural conditions. Both soil and dust aerosol samples were analyzed for their size, morphology, elemental and mineralogical composition by a number of techniques. In addition, a new technique developed by Lafon et al. (2004) has been used to determine the amount and mineralogical speciation of iron oxides in the dust samples. This information is crucial for constraining the light absorption by dust particles. The data set enables us to reconstruct several classes of representative composition-shape-size distributions required for modeling the aerosol optical characteristics following the approach of Kalashnikova and Sokolik (2004). A detailed sensitivity study was performed to assess the range of changes in optical and radiative properties of dust due to the variability in method-dependent particle size distribution, assumptions on particle shapes, and varying amount of iron oxides.