Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 4 4 2004 10.5194/acpd-4-4877-2004 http://www.atmos-chem-phys-discuss.net/4/4877/2004/ http://www.atmos-chem-phys-discuss.net/4/4877/2004/acpd-4-4877-2004.html http://www.atmos-chem-phys-discuss.net/4/4877/2004/acpd-4-4877-2004.pdf 4877 4913 2004-08-24 Impact of reactive bromine chemistry in the troposphere R. von Glasow roland.von.glasow@iup.uni-heidelberg.de R. von Kuhlmann M. G. Lawrence U. Platt P. J. Crutzen Institute for Environmental Physics, Universität Heidelberg, Germany Center for Atmospheric Sciences, Scripps Institution of Oceanography, University of California, San Diego, USA Atmospheric Chemistry Division, Max-Planck-Institut für Chemie, Mainz, Germany Recently several field campaigns and satellite observations found strong indications for bromine oxide (BrO) in the free troposphere. Using a global atmospheric chemistry transport model we show that BrO measurements mixing ratios of a few tenths to 2 pmol mol^−1 lead to a reduction in the zonal mean O₃ mixing ratio of up to 18% in widespread areas and locally even up to 40% compared to a model run without bromine chemistry. For dimethyl sulfide (DMS) the effect is even larger with up to 60% decreases. This is accompanied by dramatic changes in DMS oxidation pathways, reducing its cooling effect on climate. Changes in the HO₂:OH ratio also cause changes for NO_x and PAN. These results imply that a very strong sink for O₃ and DMS has so far been ignored in many studies of the chemistry of the troposphere.