Atmos. Chem. Phys. Discuss., 8, 9477-9530, 2008
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Consistent simulation of bromine chemistry from the marine boundary layer to the stratosphere – Part 2: Bromocarbons
A. Kerkweg1,2, P. Jöckel1, N. Warwick3, S. Gebhardt1, C.A.M. Brenninkmeijer1, and J. Lelieveld1
1Atmospheric Chemistry Department, Max Planck Institute of Chemistry, P.O.~Box 3060, 55020 Mainz, Germany
2Institute for Atmospheric Physics, University of Mainz, Germany
3University of Cambridge, Chemistry Department, Lensfield Road, Cambridge, CB2 1EW, UK

Abstract. In this second part of a series of articles dedicated to a detailed analysis of bromine chemistry in the atmosphere we address one (out of two) dominant natural sources of reactive bromine. The two main source categories are the release of bromine from sea salt and the decomposition of bromocarbons by photolysis and reaction with OH. Here, we focus on C1-bromocarbons. We show that the atmospheric chemistry general circulation model ECHAM5/MESSy realistically simulates their emission, transport and decomposition from the boundary layer up to the mesosphere. We included oceanic emission fluxes of the short-lived bromocarbons CH2Br2, CH2ClBr, CHClBr2, CHCl2Br, CHBr3 and of CH3Br. The vertical profiles and the surface mixing ratios of the bromocarbons are in general agreement with the (few available) observations, especially in view of the limited information available and the consequent coarseness of the emission fields. For CHBr3, CHCl2Br and CHClBr2 photolysis is the most important degradation process in the troposphere. In contrast to this, tropospheric CH2Br2, CH3Br and CH2ClBr are more efficiently decomposed by reaction with OH. In the free troposphere approximately one third of the C1-bromocarbons decomposes by reaction with OH. In the boundary layer the reaction with OH is relatively important, whereas it is negligible in the stratosphere. Our results indicate an approximately 50% longer lifetime of CH3Br (≈1 year) than assumed previously, implying a relatively strong contribution to stratospheric bromine and consequent ozone destruction.

Citation: Kerkweg, A., Jöckel, P., Warwick, N., Gebhardt, S., Brenninkmeijer, C.A.M., and Lelieveld, J.: Consistent simulation of bromine chemistry from the marine boundary layer to the stratosphere – Part 2: Bromocarbons, Atmos. Chem. Phys. Discuss., 8, 9477-9530, doi:10.5194/acpd-8-9477-2008, 2008.
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