1,1,1,11,2,2,4,4,6,7,7,8,12,9,10- 1Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, United Kingdom (s.arnold@leeds.ac.uk)
- 2School of Chemistry, University of Leeds, United Kingdom.
- 3National Centre for Atmospheric Sciences, University of Leeds, Leeds, LS2 9JT, United Kingdom.
- 4UCLA Atmospheric & Oceanic Sciences, Los Angeles, CA 90095, USA.
- 5Woodwell Climate Research Center, Falmouth, MA 02540, USA.
- 6Aix-Marseille Université, CNRS, LCE, Marseille, France.
- 7LATMOS/IPSL, Sorbonne Université, UVSQ, CNRS, Paris, 75252, France.
- 8Earth & Atmospheric Sciences, University of Houston, Houston, TX 77204, USA.
- 9GESTAR-II, University of Maryland Baltimore County, Baltimore, MD 21250, USA.
- 10Geophysical Institute and Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK 99775, USA.
- 11Now at: Department of Earth and Environmental Sciences, The University of Manchester, Manchester, UK.
- 12Now at: Center for Atmospheric and Environmental Chemistry, Aerodyne Research Inc, Billerica, MA 01821, USA.
The hydroxyl radical (OH) plays a key role in regulating gas-phase pollutant concentrations and particle formation and composition in the global troposphere. Globally, OH formation is dominated by production of O(1D) from photolysis of ozone and subsequent reaction with water vapour. However, under conditions characteristic of the polluted wintertime Arctic, this mechanism is inhibited by limited short-wave radiation and water abundance. A lack of observations means that our understanding of radical and oxidant sources under such conditions is lacking. The Alaskan Layered Pollution and Chemical Analysis (ALPACA) field campaign, made comprehensive measurements of trace gas and aerosol pollution chemistry and meteorology during January and February 2022 in the sub-Arctic city of Fairbanks, Alaska, USA. During the campaign, severe surface-based temperature inversions gave rise to several enhanced pollution events, interspersed with weakly stable periods of lower pollution levels and influence from the free troposphere. Here, we use the Dynamically Simple Model of Atmospheric Chemical Complexity (DSMACC) 0D box model incorporating the comprehensive Master Chemical Mechanism (MCM) v3.3.1 to quantify processes controlling the abundances of atmospheric oxidants in Fairbanks. We constrain the model using available measurements from the ALPACA campaign, and compare HOx radical sources and sinks during a strongly-stable heavily polluted period of the campaign with a less stable, cleaner period. OH formation from HONO photolysis is the major chemical source of HOx in the polluted, low-light environment of wintertime Fairbanks and formaldehyde is an important precursor for HO2. We find that the HOx budget is distinct between a polluted, strongly stable inversion event and a clean, weakly stable period, with influences of meteorology being important in regulating peroxynitric acid (PNA, HO2NO2) cycling. Our results help improve understanding of the unique atmospheric pollution chemistry that regulates oxidant abundances in cold and low-light conditions.
How to cite: Arnold, S. R., Hoffman, A., James, R., Heard, D. E., Whalley, L., Stone, D., Seldon, S., Stutz, J., Kuhn, J., Cooperdock, S., Temime-Roussel, B., Ijaz, A., D'Anna, B., Law, K. S., Bekki, S., Gou, F., Flynn, J., St Clair, J., Cesler-Maloney, M., and Simpson, W.: Photochemical modelling of wintertime HOx sources and sinks in a polluted sub-Arctic environment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14449, https://doi.org/10.5194/egusphere-egu26-14449, 2026.
