Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 2 4 2002 10.5194/acpd-2-1181-2002 http://www.atmos-chem-phys-discuss.net/2/1181/2002/ http://www.atmos-chem-phys-discuss.net/2/1181/2002/acpd-2-1181-2002.html http://www.atmos-chem-phys-discuss.net/2/1181/2002/acpd-2-1181-2002.pdf 1181 1216 2002-08-30 Sensitivity study of dimethylsulphide (DMS) atmospheric concentrations and sulphate aerosol indirect radiative forcing to the DMS source representation and oxidation O. Boucher C. Moulin S. Belviso O. Aumont L. Bopp E. Cosme R. von Kuhlmann M. G. Lawrence M. Pham M. S. Reddy J. Sciare C. Venkataraman Laboratoire d’Optique Atmosphérique, CNRS UMR 8518, USTL, Villeneuve d’Ascq, France Laboratoire des Sciences du Climat et de l’Environnement, CEA/CNRS, Gif sur Yvette, France Laboratoire d’Océanographie Dynamique et de Climatologie, CNRS/UPMC/IRD, Paris, France Laboratoire de Glaciologie et Géophysique de l’Environnement, CNRS, Saint-Martin-d’Héres, France Max Planck Institute for Chemistry, Air Chemistry Department, Mainz, Germany Service d’Aéronomie, CNRS/UPMC/UVSQ, Paris, France Centre for Environmental Science and Engineering, Indian Institute of Technology, Bombay, India The global sulphur cycle has been simulated using a general circulation model with a focus on the source and oxidation of atmospheric dimethylsulphide (DMS). The sensitivity of atmospheric DMS to the oceanic DMS climatology, the parameterisation of the sea-air transfer and to the oxidant fields have been studied. The importance of additional oxidation pathways (by O₃ in the gas- and aqueous-phases and by BrO in the gas phase) not incorporated in global models has also been evaluated. While the global DMS flux is well constrained at 24-27 Tg S yr ^-1, there are large differences in the spatial and seasonal distribution of the atmospheric DMS flux generated from the three climatologies of oceanic DMS considered here. The relative contributions of OH and NO₃ radicals to DMS oxidation depends critically on which oxidant fields are prescribed in the model. Oxidation by O₃ appears to be significant at high latitudes in both hemispheres. Oxidation by BrO could be significant even for BrO concentrations at sub-pptv levels in the marine boundary layer.