Investigation of Cloud Nucleation Activity of Regional Dust Samples using Adsorption Activation Theory and CCN Measurements

Mineral dust aerosols play an important role in warm clouds due to their ability to serve as effective Cloud Condensation Nuclei (CCN). However, predicting the complex effect of mineral dusts on clouds and climate requires integrating observational knowledge into theoretical mathematical parameterizations. Current climate models, use traditional Köhler theory to describe supersaturation required for dust activation based on its soluble fraction, ignoring the hydrophilic interactions of the "insoluble" core with water vapor.

In this work, we present improvements in current understanding of mineral dusts interactions with clouds by coupling laboratory CCN activation measurements of regional dust samples with advancements in numerical parameterizations to describe dust-cloud interactions in global aerosol climate models. The mineral dusts investigated include samples from Northern America, African, and East Asian soils. To assess the role of the mineralogy on dust CCN activity, we also perform measurements with the most abundant individual minerals (clays and carbonates). The results obtained from these measurements are used to constrain a new droplet formation parameterization that explicitly accounts for "adsorption activation" using the multilayer Frenkel-Halsey-Hill (FHH) adsorption isotherm model modified to account for particle curvature (Kumar et al., 2009). A comparison of different aerosol-water vapor interaction mechanisms (traditional Köhler theory vs adsorption activation theory) is then carried out focusing on the potential differences in CCN number, parcel maximum supersaturation and cloud droplet number.