Modelling wintertime sea-spray aerosols under Arctic haze conditions

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Ioannidis, Eleftherios, Law, Kathy S., Raut, Jean-Christophe, Marelle, Louis, Onishi, Tatsuo, Kirpes, Rachel M., Upchurch, Lucia M., Tuch, Thomas, Wiedensohler, Alfred, Massling, Andreas, Skov, Henrik, Quinn, Patricia K., Pratt, Kerri A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2023
• Subjects: article; Verlagsveröffentlichung; Arctic; Barrow; Alaska
• Online Access: https://doi.org/10.5194/acp-23-5641-2023; https://noa.gwlb.de/receive/cop_mods_00066536; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00065017/acp-23-5641-2023.pdf; https://acp.copernicus.org/articles/23/5641/2023/acp-23-5641-2023.pdf

Anthropogenic and natural emissions contribute to enhanced concentrations of aerosols in the Arctic winter and early spring, with most attention being paid to anthropogenic aerosols that contribute to so-called Arctic haze. Less-well-studied wintertime sea-spray aerosols (SSAs) under Arctic haze conditions are the focus of this study, since they can make an important contribution to wintertime Arctic aerosol abundances. Analysis of field campaign data shows evidence for enhanced local sources of SSAs, including marine organics at Utqiaġvik (formerly known as Barrow) in northern Alaska, United States, during winter 2014. Models tend to underestimate sub-micron SSAs and overestimate super-micron SSAs in the Arctic during winter, including the base version of the Weather Research Forecast coupled with Chemistry (WRF-Chem) model used here, which includes a widely used SSA source function based on Gong et al. (1997). Quasi-hemispheric simulations for winter 2014 including updated wind speed and sea-surface temperature (SST) SSA emission dependencies and sources of marine sea-salt organics and sea-salt sulfate lead to significantly improved model performance compared to observations at remote Arctic sites, notably for coarse-mode sodium and chloride, which are reduced. The improved model also simulates more realistic contributions of SSAs to inorganic aerosols at different sites, ranging from 20 %–93 % in the observations. Two-thirds of the improved model performance is from the inclusion of the dependence on SSTs. The simulation of nitrate aerosols is also improved due to less heterogeneous uptake of nitric acid on SSAs in the coarse mode and related increases in fine-mode nitrate. This highlights the importance of interactions between natural SSAs and inorganic anthropogenic aerosols that contribute to Arctic haze. Simulation of organic aerosols and the fraction of sea-salt sulfate are also improved compared to observations. However, the model underestimates episodes with elevated observed concentrations of SSA ...