(682d) The Importance of Adsorption Activation for Mineral Dust and CCN Activity of Diverse Regional Dust Samples

Mineral dust aerosols represent a dominant source of particulate (by mass) in the atmosphere and have been found to play important role in warm clouds due to their ability to serve as effective Cloud Condensation Nuclei (CCN). Current climate models, use traditional Köhler theory to describe supersaturation required for dust activation based on its soluble fraction, and completely ignore interactions of hydrophilic insoluble core with water vapor even in appreciable. In this study, we address the activation of hydrophilic insoluble dust particle using multilayer Frenkel-Halsey-Hill (FHH) adsorption isotherm model modified to account for particle curvature. A comparison of different aerosol-water vapor interaction mechanisms for cloud droplet formation suggests that traditional Köhler theory can lead to substantial differences in parcel supersaturation and cloud droplet number to that predicted by the adsorption activation framework. A comparison based on the CCN spectra of different mineral dusts suggests that the traditional Köhler theory overestimates the CCN number relative to that predicted by multilayer physical adsorption models.

We also investigate the CCN-relevant properties of mineral dust samples representative of major regional dust sources using the Continuous-Flow Streamwise Thermal Gradient CCN Counter (CCNc). The CCN activation behavior of mineral dusts from Northern America, African soils, and East Asian soils are studied experimentally in the laboratory condition to determine their respective affinity to water. In parallel, CCN activities of various individual minerals (such as clays and carbonates) are compared with regional dust samples, to assess the role of the mineralogical composition of dust samples on their CCN activity. This new framework of aerosol-water interaction by the ?adsorption activation? has been incorporated into aerosol-cloud interaction parameterizations for mineral dust activation.