Impact of reactive bromine chemistry in the troposphere

Abstract

Abstract. 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 NOx 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.