Shallow boundary layer heights controlled by the surface-based temperature inversion strength are responsible for trapping home heating emissions near the ground level in Fairbanks, Alaska
Abstract. In cold climate cities, like Fairbanks, Alaska, during winter, reduced vertical mixing in the atmosphere leads to pollution trapping and concerningly high PM2.5 concentrations at ground level. To study pollution trapping, we simulated dispersion of SO2 from home heating emissions during the ALPACA-2022 field study in Fairbanks, Alaska using the Platform for Atmospheric Chemistry and Transport one-dimensional model (PACT-1D). Eddy diffusion coefficients that control vertical transport were parameterized by the near-surface temperature inversion strength according to stable boundary layer (SBL) theory and horizontal export was calculated from the wind speed. The model parameterized the SBL height as a function of the near-surface inversion strength, with the SBL height varying between 50 m for weak inversions down to 20 m for strong inversions. The model results were compared to long-path differential optical absorption spectroscopy (LP-DOAS) concentration profiles and in-situ observations of SO2 over the range of 3 m to 191 m above downtown Fairbanks over a 33-day period in winter and achieved excellent agreement (R = 0.88). Sensitivity studies showed that the model is most sensitive to the SBL height and the associated eddy diffusivity profile. Model-derived pollution residence times in Fairbanks are on the order of hours during winter, with a median steady state residence time of 2.1 hours under stable atmospheric conditions, indicating there is limited time for chemical processing.
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Gas and meteorological measurements at the CTC site and Birch Hill in Fairbanks, Alaska, during the ALPACA-2022 field study https://doi.org/10.18739/A27D2Q87W
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