DMS and SO2 at Baring Head, New Zealand: Implications for the yield of SO2 from DMS

Atmospheric dimethyl sulfide (DMS) and sulfur dioxide (SO2) concentrations were measured at Baring Head, New Zealand during February and March 2000. Anti-correlated DMS and SO2 diurnal cycles, consistent with the photochemical production of SO2 from DMS, were observed in clean southerly air off the ocean. The data is used to infer a yield of SO2 from DMS oxidation. The estimated yields are highly dependent on assumptions about the DMS oxidation rate. Fitting the measured data in a photochemical box model using model-generated OH levels and the Hynes et al. (1986) DMS + OH rate constant suggests that the SO2 yield is 50-100%, similar to current estimates for the tropical Pacific. However, the observed amplitude of the DMS diurnal cycle suggests that the oxidation rate is higher than that used by the model, and therefore, that the SO2 yield is lower in the range of 20-40%