The concentration and distribution of dimethyl sulfide in the marine atmospheric boundary layer near the equator

A one-dimensional photochemical model with parameterized vertical eddy diffusion is used to simulate the dimethyl sulfide (DMS) in the marine atmospheric boundary layer near the equator.The boundary condition of the DMS flux over sea surface is assigned from gas exchange models that depend on sea surface wind speed and DMS concentration in surface water.Photolysis rates at various altitudes are calculated as a function of solar zenith angle, and the radiation calculation includes ozone absorption, surface reflection and molecular scattering.
The simulated results of the DMS diurnal cycle are in good agreement with the observations.Sensitivity tests of the model indicate that the concentration of the DMS in the marine surface layer appears to be affected by a combination of chemical processes and meteorological conditions.In addition, photochemical processes are rather important.The reaction of the DMS with.OH radical, the heterogeneous conversion of SO₂ and the deposition of NSS-SO₄^- and the methanesulfonic acid (MSA) are critical factors of controlling the DMS, SO₂, NSS-SO₄^- and the MSA concentrations and distributions in the atmosphere.The DMS concentration in air is directly proportional to surface wind speed, but it is inversely proportional to boundary layer height in the convective boundary layer.The distributions of the DMS concentrations in sir are strongly influenced by atmospheric stratification in stable conditions.