Effective Refractive Index Retrieval and Single Scattering Albedo Implications of Dry-Generated Mineral Dust Component Aerosol

There is much uncertainty in the contribution of mineral dust and clay aerosol to climate forcing, especially as related to the non-spherical shape and rough surface of the particles. A laboratory method for retrieving effective refractive indices of a series of mineral dust component aerosol based on extinction as a function of size is explored. Clay and other mineral dust component aerosols were produced via an improved stability, dry-generation method to more closely capture natural emission mechanisms in comparison to typical wet-generation. Aerosol size was determined via tandem differential mobility analysis, and optical extinction was measured with a cavity ring-down spectrometer at 532 nm. The effective refractive index values assume a spherical model and are obtained through fitting the measured data of non-spherical aerosol. The effective and literature bulk refractive index values were then used to calculate single scattering albedo, which shows the changed warming potential with the new effective values for some samples. Further, the impact that grinding the sample before generation has on the observed optical properties was quantified. These results may be used to refine the inclusion of dust components in climate models.