Implementation and Impacts of Surface and Blowing Snow Sources of Arctic Bromine Activation Within WRF‐Chem 4.1.1. (30th July 2021)

• Record Type: Journal Article
• Authors: Marelle, Louis; Thomas, Jennie L.; Ahmed, Shaddy; Tuite, Katie; Stutz, Jochen; Dommergue, Aurélien; Simpson, William R.; Frey, Markus M.; Baladima, Foteini
• Is Part Of: Journal of advances in modeling earth systems. Volume 13:Number 8(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-07-30
• Subjects: aerosol chemistry -- arctic ozone -- atmospheric chemistry -- halogen chemistry -- snow emissions; Geological modeling -- Periodicals; Climatology -- Periodicals; Geochemical modeling -- Periodicals; 551.5011
• DOI: 10.1029/2020MS002391
• Languages: English
• ISSNs: 1942-2466

Abstract

Abstract: Elevated concentrations of atmospheric bromine are known to cause ozone depletion in the Arctic, which is most frequently observed during springtime. We implement a detailed description of bromine and chlorine chemistry within the WRF‐Chem 4.1.1 model, and two different descriptions of Arctic bromine activation: (1) heterogeneous chemistry on surface snow on sea ice, triggered by ozone deposition to snow (Toyota et al., 2011 https://doi.org/10.5194/acp-11-3949-2011 ), and (2) heterogeneous reactions on sea salt aerosols emitted through the sublimation of lofted blowing snow (Yang et al., 2008, https://doi.org/10.1029/2008gl034536 ). In both mechanisms, bromine activation is sustained by heterogeneous reactions on aerosols and surface snow. Simulations for spring 2012 covering the entire Arctic reproduce frequent and widespread ozone depletion events, and comparisons with observations of ozone show that these developments significantly improve model predictions during the Arctic spring. Simulations show that ozone depletion events can be initiated by both surface snow on sea ice, or by aerosols that originate from blowing snow. On a regional scale, in spring 2012, snow on sea ice dominates halogen activation and ozone depletion at the surface. During this period, blowing snow is a major source of Arctic sea salt aerosols but only triggers a few depletion events. Plain Language Summary: During Arctic spring, ground level ozone is often depleted to very low concentrations compared to background levels. This surface ozone depletion is caused by reactive halogen species in the atmosphere, especially bromine. In this study, we implement a detailed description of chlorine and bromine chemistry in the regional atmospheric model WRF‐Chem 4.1.1. We also compare two different bromine sources capable of triggering these events: first, chemical reactions on surface snow over sea ice, and second, sea salt particles emitted by the sublimation of salty "blowing snow" lofted by strong winds. These developments are used to investigate the origins of Arctic bromine and of ozone depletion events, and to improve the representation of Arctic ozone in the model. We find that, in spring 2012, both bromine sources can cause ozone depletion events, but that over the entire Arctic, snow on sea ice dominates halogen activation and causes ground level ozone depletion. Key Points: Halogen activation and its role in Arctic surface ozone depletion events (ODEs) is modeled using WRF‐Chem Two halogen activation mechanisms are implemented (1) surface snow and (2) blowing snow A spring 2012 case study indicates that both mechanisms can trigger near‐surface ODEs, but that surface snow dominates