Mesoscale modeling of DMS emission and transport processes during ACE-1

C.Mari, K.Suhre, T.Bates, J.Johnson, R.Rosset
Laboratoire d'Aerologie, TOULOUSE, FRANCE

Atmospheric DMS concentrations are strongly dependent on the heterogeneity of DMS distribution in seawater, transport by mesoscale meteorological events such as cold fronts and chemical sink (mainly oxidation by OH) The aim of our study is to assess the relative influence of these different processes on observed atmospheric DMS during ACE-1 experiment. For this purpose, a 3D mesoscale non hydrostatic model including fractional cloudiness, cloud microphysics, turbulence scheme (1.5 order closure), diagnostic tools, online diffusion and transport of scalars, is used to simulate DMS emission, transport and chemical destruction. The model is initialized using ECMWF analyses and is validated using satellite images. Simulations are done, starting prior to Lagrangian B intensive observational period, thus including the transition from cold front to clear postfrontal air. Several scenarios are tested to analyse the impact of these frontal 3D event on passive tracers re-distribution in the troposphere. This knowledge is then applied to the study of DMS vertical and horizontal transport in the ACE-1 region. Different DMS sea-to-air flux parameterisations are tested, using a 2D interpolated spatial distribution of seawater DMS concentrations measured on board R/V Discoverer, and winds provided by the model. Preliminary results about sensitivity studies on these coupled processes are presented.