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Transported African Wildfire Smoke Acts as Cloud Condensation Nuclei in the Tropical Atlantic Marine Boundary Layer
HALEY ROYER, Mira L. Pöhlker, Ovid O. Krüger, Edmund Blades, Peter Sealy, Nurun Nahar Lata, Zezhen Cheng, Swarup China, Andrew Ault, Patricia Quinn, Hope Elliott, Patricia Blackwelder, Cassandra Gaston, University of Miami
Abstract Number: 281
Working Group: Wildfire Aerosols
Abstract
The role of aerosols on cloud formation in the tropical Atlantic is important to understand as marine stratocumulus clouds reflect incoming solar radiation and obscure the low-albedo ocean surface. However, few studies have been conducted on aerosol-cloud interactions in this region. Ragged Point–a research station situated in Barbados–was established to study aerosol transport to the Caribbean including the summertime transport of African dust. The site is also uniquely situated to study cloud-aerosol interactions in the tropical Atlantic. In this study, we compared size-resolved chemical data from computer-controlled scanning electron microscopy coupled with energy dispersive x-ray spectroscopy (CCSEM/EDS) to size-resolved CCN measurements from a cloud condensation nuclei (CCN) counter (CCNC) coupled with a scanning mobility particle sizer (SMPS). Data were collected at the Ragged Point field station during the EUREC4A and ATOMIC campaigns from January to February 2020. Results show unusual wintertime transport of African smoke and dust to the northwest tropical Atlantic. When long-range transported African aerosol arrived in Barbados, we observed a compositional change in the aerosol particle loading from marine sulfate to smoke particles as well as a decrease in aerosol hygroscopicity. Further, during these time periods, CCN number concentrations doubled, suggesting that transported smoke particles increase the CCN burden compared to marine background conditions. Previous research has shown the impact of African smoke on clouds over the tropical south Atlantic. However, our work shows that aerosol hygroscopicity and CCN number concentrations over the tropical North Atlantic are also affected by African smoke. These findings highlight the pervasive impact of African smoke in the Atlantic marine boundary layer and can be used to improve uncertainties in current climate models regarding the role of smoke particles on cloud formation and cloud properties in the tropical North Atlantic.