African smoke particles act as cloud condensation nuclei in the wintertime tropical North Atlantic boundary layer over Barbados

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Royer, Haley M., Pöhlker, Mira L., Krüger, Ovid, Blades, Edmund, Sealy, Peter, Lata, Nurun Nahar, Cheng, Zezhen, China, Swarup, Ault, Andrew P., Quinn, Patricia K., Zuidema, Paquita, Pöhlker, Christopher, Pöschl, Ulrich, Andreae, Meinrat, Gaston, Cassandra J.
• Format: Text
• Language: English
• Published: 2023
• Subjects: North Atlantic
• Online Access: https://doi.org/10.5194/acp-23-981-2023; https://acp.copernicus.org/articles/23/981/2023/

The number concentration and properties of aerosol particles serving as cloud condensation nuclei (CCN) are important for understanding cloud properties, including in the tropical Atlantic marine boundary layer (MBL), where marine cumulus clouds reflect incoming solar radiation and obscure the low-albedo ocean surface. Studies linking aerosol source, composition, and water uptake properties in this region have been conducted primarily during the summertime dust transport season, despite the region receiving a variety of aerosol particle types throughout the year. In this study, we compare size-resolved aerosol chemical composition data to the hygroscopicity parameter κ derived from size-resolved CCN measurements made during the Elucidating the Role of Clouds–Circulation Coupling in Climate (EUREC 4 A) and Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC) campaigns from January to February 2020. We observed unexpected periods of wintertime long-range transport of African smoke and dust to Barbados. During these periods, the accumulation-mode aerosol particle and CCN number concentrations as well as the proportions of dust and smoke particles increased, whereas the average κ slightly decreased ( <math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi mathvariant="italic">κ</mi><mo>=</mo><mn mathvariant="normal">0.46</mn><mo>±</mo><mn mathvariant="normal">0.10</mn></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="75pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="b409514c275386595bca636d92c5f342"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-981-2023-ie00001.svg" width="75pt" height="10pt" src="acp-23-981-2023-ie00001.png"/></svg:svg> ) from marine background conditions ( <math xmlns="http://www.w3.org/1998/Math/MathML" id="M5" display="inline" overflow="scroll" ...