Impact of reactive bromine chemistry in the troposphere

[摘要] Recently several field campaigns and satellite observations have foundstrong indications for the presence of bromine oxide (BrO) inthe free troposphere.Using a global atmospheric chemistry transportmodel we show that BrO mixing ratios of a few tenths to 2 pmol mol^-1 lead to a reduction in the zonal mean O₃ mixingratio of up to 18% in widespread areas and regionally up to 40%compared to a model run without bromine chemistry. A lower limitapproach for the marine boundary layer, that does not explicitlyinclude the release of halogens from sea salt aerosol, shows that fordimethyl sulfide (DMS) the effect is even larger, with up to60% reduction of its tropospheric column.This is accompanied bydramatic changes in DMS oxidation pathways, reducing its coolingeffect on climate.In addition there are changes in the HO₂:OH ratio that also affect NO_x and PAN.Theseresults imply that potentially significant strong sinks for O₃and DMS have so far been ignored in many studies of thechemistry of the troposphere.

[学科分类] 大气科学