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Intercomparison Between Surrogate, Explicit, and Full Treatments of VSL Bromine Chemistry Within the CAM-Chem
Rafael P Fernandez1,2,3,4, Javier A Barrera2,3, Ana Isabel López-Noreña3,4
1Department of Atmospheric Chemistry and Climate Institute of Physical Chemistry Rocasolano CSIC Madrid Spain.
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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