Arctic tropospheric ozone: assessment of current knowledge and model performance

• Published in: Atmospheric Chemistry and Physics
• Main Authors: C. H. Whaley, K. S. Law, J. L. Hjorth, H. Skov, S. R. Arnold, J. Langner, J. B. Pernov, G. Bergeron, I. Bourgeois, J. H. Christensen, R.-Y. Chien, M. Deushi, X. Dong, P. Effertz, G. Faluvegi, M. Flanner, J. S. Fu, M. Gauss, G. Huey, U. Im, R. Kivi, L. Marelle, T. Onishi, N. Oshima, I. Petropavlovskikh, J. Peischl, D. A. Plummer, L. Pozzoli, J.-C. Raut, T. Ryerson, R. Skeie, S. Solberg, M. A. Thomas, C. Thompson, K. Tsigaridis, S. Tsyro, S. T. Turnock, K. von Salzen, D. W. Tarasick
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2023
• Subjects: Physics; QC1-999; Chemistry; QD1-999; Arctic; Eureka; Human health
• Online Access: https://doi.org/10.5194/acp-23-637-2023; https://doaj.org/article/8babaa457d7d4068bac1dd5438b4d0e2

As the third most important greenhouse gas (GHG) after carbon dioxide (CO 2 ) and methane ( CH 4 ), tropospheric ozone (O 3 ) is also an air pollutant causing damage to human health and ecosystems. This study brings together recent research on observations and modeling of tropospheric O 3 in the Arctic, a rapidly warming and sensitive environment. At different locations in the Arctic, the observed surface O 3 seasonal cycles are quite different. Coastal Arctic locations, for example, have a minimum in the springtime due to O 3 depletion events resulting from surface bromine chemistry. In contrast, other Arctic locations have a maximum in the spring. The 12 state-of-the-art models used in this study lack the surface halogen chemistry needed to simulate coastal Arctic surface O 3 depletion in the springtime; however, the multi-model median (MMM) has accurate seasonal cycles at non-coastal Arctic locations. There is a large amount of variability among models, which has been previously reported, and we show that there continues to be no convergence among models or improved accuracy in simulating tropospheric O 3 and its precursor species. The MMM underestimates Arctic surface O 3 by 5 % to 15 % depending on the location. The vertical distribution of tropospheric O 3 is studied from recent ozonesonde measurements and the models. The models are highly variable, simulating free-tropospheric O 3 within a range of ±50 % depending on the model and the altitude. The MMM performs best, within ±8 % for most locations and seasons. However, nearly all models overestimate O 3 near the tropopause ( ∼300 hPa or ∼8 km), likely due to ongoing issues with underestimating the altitude of the tropopause and excessive downward transport of stratospheric O 3 at high latitudes. For example, the MMM is biased high by about 20 % at Eureka. Observed and simulated O 3 precursors (CO, NO x , and reservoir PAN) are evaluated throughout the troposphere. Models underestimate wintertime CO everywhere, likely due to a combination of ...