Regional Transport in the Arctic: Sensitivity of NOₓ and Particulate Matter in Wintertime Urban Alaska to Background Air

Fairbanks, Alaska is an example of a subarctic city that experiences severe wintertime air quality episodes characterized by high concentrations of fine particulate matter (PM₂.₅ ) and nitrogen oxides (NO and NO₂ = NOₓ). Previous research into these air quality episodes has focused on the impact of surface‐based inversions that trap local emissions. However, the availability of ozone is a limiting factor in local wintertime pollutant transformation, and sensitivity of Fairbanks air quality to ozone availability has not been investigated on a regional scale. Here, we assess the impact of regional transport on ozone, NOₓ, and particulate matter concentrations in Fairbanks, Alaska using three boundary conditions in the Community Multiscale Air Quality (CMAQ) model v5.4. We compared model results with measurements made during the ALPACA field campaign (model‐observation comparison), and we assessed the differences between pairs of models (model‐model comparison) using Euclidean distances of NO₂ , SO₂, PM₂.₅, and O₃. We find that modeling of NO x in the Fairbanks area depends on, amongst other factors, accurate boundary conditions of background ozone because NO + O₃ titration is the dominant loss reaction of NO. PM₂.₅ in Fairbanks is affected by transport of existing background particulate matter rather than the transport of precursors. The boundary condition transport impacts metrics of air pollutants used for regulatory purposes throughout the model domain. Our results have important implications for accurate modeling of air quality in Arctic regions subject to strong local emissions and surface‐based inversions, and have implications for assessment of air quality attainment status.