The role of snow in controlling halogen chemistry and boundary layer oxidation during Arctic spring: A 1D modeling case study

Reactive chlorine and bromine species emitted from snow and aerosols can significantly alter the oxidative capacity of the polar boundary layer. However, halogen production mechanisms from snow remain highly uncertain, making it difficult for most models to include descriptions of halogen snow emissions and to understand the impact on atmospheric chemistry. We investigate the influence of Arctic halogen emissions from snow on boundary layer oxidation processes using a one-dimensional atmospheric chemistry and transport model (PACT-1D). To understand the combined impact of snow emissions and boundary layer dynamics on atmospheric chemistry, we model Cl-2 and Br-2 primary emissions from snow and include heterogeneous recycling of halogens on both snow and aerosols. We focus on a 2-day case study from the 2009 Ocean-Atmosphere-Sea Ice-Snowpack campaign at Utqia x121;vik, Alaska. The model reproduces both the diurnal cycle and high quantity of Cl-2 observed, along with the measured concentrations of Br-2, BrO, and HOBr. Due to the combined effects of emissions, recycling, vertical mixing, and atmospheric chemistry, reactive chlorine is typically confined to the lowest 15 m of the atmosphere, while bromine can impact chemistry up to and above the surface inversion height. Upon including halogen emissions and recycling, the concentration of HOx (HOx = OH + HO2) at the surface increases by as much as a factor of 30 at mid-day. The change in HOx due to halogen chemistry, as well as chlorine atoms derived from snow emissions, significantly reduce volatile organic compound lifetimes within a shallow layer near the surface.

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Related Links

Related Dataset #1 : Daily pan-Arctic sea-ice lead maps for 2003-2015, with links to maps in NetCDF format

Related Dataset #2 : Aerosol measurements during OASIS Barrow field intensive Spring 2009, Version 1.0

Related Dataset #3 : Ozone, NOx, and NOy measurements during OASIS Barrow field intensive Spring 2009, Version 1.0

Related Dataset #4 : CESM2.1/CAM-chem Instantaneous Output for Boundary Conditions

Related Dataset #5 : PACT-1D model version including polar halogen emissions - output files

Related Software #1 : PACT1D/PACT-1D-HALOGENS: PACT-1D model (v1.1) including polar chlorine and bromine emission mechanisms

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Author Ahmed, S.
Thomas, J. L.
Tuite, K.
Stutz, J.
Flocke, Frank M.
Orlando, John J.
Hornbrook, Rebecca
Apel, Eric C.
Emmons, Louisa K.
Helmig, D.
Boylan, P.
Huey, L. G.
Hall, Samuel R.
Ullmann, Kirk
Cantrell, C. A.
Fried, Alan
Publisher UCAR/NCAR - Library
Publication Date 2022-03-16T00:00:00
Digital Object Identifier (DOI) Not Assigned
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Topic Category geoscientificInformation
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Metadata Date 2025-07-11T16:05:25.981640
Metadata Record Identifier edu.ucar.opensky::articles:25268
Metadata Language eng; USA
Suggested Citation Ahmed, S., Thomas, J. L., Tuite, K., Stutz, J., Flocke, Frank M., Orlando, John J., Hornbrook, Rebecca, Apel, Eric C., Emmons, Louisa K., Helmig, D., Boylan, P., Huey, L. G., Hall, Samuel R., Ullmann, Kirk, Cantrell, C. A., Fried, Alan. (2022). The role of snow in controlling halogen chemistry and boundary layer oxidation during Arctic spring: A 1D modeling case study. UCAR/NCAR - Library. https://n2t.org/ark:/85065/d7qj7mxc. Accessed 01 August 2025.

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