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Intercomparison Between Surrogate, Explicit, and Full Treatments of VSL Bromine Chemistry Within the CAM-Chem Chemistry-Climate Model

Rafael P. Fernandez, Javier A. Barrera, Ana Isabel López-Noreña, Douglas E. Kinnison, Julie Nicely, Ross J. Salawitch, Pamela A. Wales, Beatriz M. Toselli, Simone Tilmes, Jean-François Lamarque, Carlos A. Cuevas, and Alfonso Saiz-Lopez.

Geophysical Research Letter, Volume 48, Issue 4, https://doi.org/10.1029/2020GL091125, 2021.

Abstract:

Many Chemistry‐Climate Models (CCMs) include a simplified treatment of brominated very short‐lived (VSLBr) species by assuming CH3Br as a surrogate for VSLBr. However, neglecting a comprehensive treatment of VSLBr in CCMs may yield an unrealistic representation of the associated impacts. Here, we use the Community Atmospheric Model with Chemistry (CAM‐Chem) CCM to quantify the tropospheric and stratospheric changes between various VSLBr chemical approaches with increasing degrees of complexity (i.e., surrogate, explicit, and full). Our CAM‐Chem results highlight the improved accuracy achieved by considering a detailed treatment of VSLBr photochemistry, including sea‐salt aerosol dehalogenation and heterogeneous recycling on ice‐crystals. Differences between the full and surrogate schemes maximize in the lowermost stratosphere and midlatitude free troposphere, resulting in a latitudinally dependent reduction of ∼1–7 DU in total ozone column and a ∼5%–15% decrease of the OH/HO2 ratio. We encourage all CCMs to include a complete chemical treatment of VSLBr in the troposphere and stratosphere.

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