Using Novel Molecular-Level Chemical Composition Observations of High Arctic Organic Aerosol for Predictions of Cloud Condensation Nuclei

• Published in: Environmental Science & Technology
• Main Authors: Siegel, Karolina, Neuberger, Almuth, Karlsson, Linn, Zieger, Paul, Mattsson, Fredrik, Duplessis, Patrick, Dada, Lubna, Daellenbach, Kaspar, Schmale, Julia, Baccarini, Andrea, Krejci, Radovan, Svenningsson, Birgitta, Chang, Rachel, Ekman, Annica M.L., Riipinen, Ilona, Mohr, Claudia
• Format: Article in Journal/Newspaper
• Language: English
• Published: The American Chemical Society (ACS) 2022
• Subjects: Meteorology and Atmospheric Sciences; aerosol chemistry; aerosol-cloud interactions; atmospheric aerosol; CCN closure; chemical ionization mass spectrometry (CIMS); cloud droplet activation; High Arctic; Arctic; Arctic Ocean; oden
• Online Access: https://lup.lub.lu.se/record/2eae2ef9-f093-46d7-ae2e-029205ecae39; https://doi.org/10.1021/acs.est.2c02162

Predictions of cloud droplet activation in the late summertime (September) central Arctic Ocean are made using κ-Kohler theory with novel observations of the aerosol chemical composition from a high-resolution time-of-flight chemical ionization mass spectrometer with a filter inlet for gases and aerosols (FIGAERO-CIMS) and an aerosol mass spectrometer (AMS), deployed during the Arctic Ocean 2018 expedition onboard the Swedish icebreaker Oden. We find that the hygroscopicity parameter κ of the total aerosol is 0.39 ± 0.19 (mean ± std). The predicted activation diameter of ∼25 to 130 nm particles is overestimated by 5%, leading to an underestimation of the cloud condensation nuclei (CCN) number concentration by 4-8%. From this, we conclude that the aerosol in the High Arctic late summer is acidic and therefore highly cloud active, with a substantial CCN contribution from Aitken mode particles. Variability in the predicted activation diameter is addressed mainly as a result of uncertainties in the aerosol size distribution measurements. The organic κ was on average 0.13, close to the commonly assumed κ of 0.1, and therefore did not significantly influence the predictions. These conclusions are supported by laboratory experiments of the activation potential of seven organic compounds selected as representative of the measured aerosol.