DMS atmospheric concentrations and sulphate aerosol indirect radiative forcing: a sensitivity study to the DMS source representation and oxidation

[摘要] The global sulphur cycle has been simulated using a general circulation modelwith a focus on the source and oxidation of atmospheric dimethylsulphide (DMS). The sensitivity of atmospheric DMS to the oceanic DMS climatology, theparameterisation of the sea-air transfer and to the oxidant fields have beenstudied. The importance of additional oxidation pathways (by O₃ in thegas- and aqueous-phases and by BrO in the gas phase) not incorporated in global models has also been evaluated. While three different climatologies ofthe oceanic DMS concentration produce rather similar global DMS fluxes to theatmosphere at 24-27 Tg S yr ^-1, there are large differences in thespatial and seasonal distribution. The relative contributions of OH and NO₃ radicals to DMS oxidation depends critically on which oxidant fieldsare prescribed in the model. Oxidation by O₃ appears to be significant athigh latitudes in both hemispheres. Oxidation by BrO could be significant even for BrO concentrations at sub-pptv levels in the marine boundary layer.The impact of such refinements on the DMS chemistry onto the indirect radiative forcing by anthropogenic sulphate aerosols is also discussed.

[学科分类] 大气科学