Influence of dust composition on cloud droplet formation

Abstract

Previous studies suggest that interactions between dust particles and clouds are significant; yet the conditions where dust particles can serve as cloud condensation nuclei (CCN) are uncertain. Since major dust components are insoluble, the CCN activity of dust strongly depends on the presence of minor components. However, many minor components measured in dust particles are overlooked in cloud modeling studies. Some of these compounds are believed to be products of heterogeneous reactions involving carbonates. In this study, we calculate with diameters between about 0.6 and 2 µm under some conditions. Dust particles > 2 µm often activate regardless of their composition. Only under very specialized conditions does the addition of a dust distribution into a rising parcel containing fine (NH 4 ) 2 SO 4 particles significantly reduce the total number of activated particles via water competition. Effects of dust on cloud saturation and droplet number via water competition are generally smaller than those reported previously for sea salt. Large numbers of fine dust CCN can significantly enhance the number of activated particles under certain conditions. Improved representations of dust mineralogy and reactions in global aerosol models could improve predictions of the effects of aerosol on climate.

Estimation of cloud condensation nuclei concentration from aerosol optical quantities: influential factors and uncertainties

“…CN concentrations at the NIM site are the largest because dust events are frequent. The ability of dust particles to serve as CCN strongly depends on the amount of minor soluble substances contained in the dust particles Kelly et al, 2007). CCN generally increases with CN during dust events, but the ratio of CCN to CN tends to decrease sharply with increasing CN, implying that less CCN become available under dusty conditions .…”

Observation of nitrate coatings on atmospheric mineral dust particles

“…Mineral dust particles with nitrate coatings are hydrophilic, and those without coating are commonly hydrophobic (Kelly et al, 2007;Shi et al, 2008). The deliquescence relative humidities (DRHs) of hydrated Ca(NO 3 ) 2 and Mg(NO 3 ) 2 are ∼12% and ∼11%, respectively (Tang and Fung, 1997;Li et al, 2008).…”

“…When aged by soluble aerosol components, these mineral particles will have enhanced hygroscopicity and altered sizes and shapes (Krueger et al, 2003(Krueger et al, , 2004Laskin et al, 2005b). As a result, the coated dust particles become more efficient CCN (Kelly et al, 2007). Therefore, knowledge about the soluble components coated on mineral particles is important for evaluating their impact on both global and regional climates.…”

Impact of mineral dust on nitrate, sulfate, and ozone in transpacific Asian pollution plumes

“…A shift of nitrate or sulfate towards larger particle sizes can change their direct radiative forcing characteristics (Liao and Seinfeld, 2005;Kim et al, 2004). In addition, coating of dust with soluble nitrate or sulfate can enhance its cloud condensation nuclei potential (Kelly et al, 2007), while reducing its ice nuclei efficiency (Koehler et al, 2007), with consequences for cloud properties and precipitation (Rosenfeld et al, 2001;Fan et al, 2004).…”