Arctic tropospheric ozone: assessment of current knowledge and model performance

• Main Authors: Whaley, Cynthia H., Law, Kathy S., Hjorth, Jens Liengaard, Skov, Henrik, Arnold, Stephen R., Langner, Joakim, Pernov, Jakob Boyd, Chien, Rong-You, Christensen, Jesper H., Deushi, Makoto, Dong, Xinyi, Faluvegi, Gregory, Flanner, Mark, Fu, Joshua S., Gauss, Michael, Im, Ulas, Marelle, Louis, Onishi, Tatsuo, Oshima, Naga, Plummer, David A., Pozzoli, Luca, Raut, Jean-Christophe, Skeie, Ragnhild, Thomas, Manu A., Tsigaridis, Kostas, Tsyro, Svetlana, Turnock, Steven T., Salzen, Knut, Tarasick, David W.
• Format: Text
• Language: English
• Published: 2022
• Subjects: Arctic; Eureka; Human health
• Online Access: https://doi.org/10.5194/acp-2022-319; https://acp.copernicus.org/preprints/acp-2022-319/

As the third most important greenhouse gas (GHG) after CO 2 and methane, 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 reported previously, and we show that there continues to be no convergence among models, nor 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 % at 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 underestimating CO emissions and ...