This work aims at better understanding the atmospheric sulfur cycle in Antarctica through the use of an Atmospheric General Circulation Model (AGCM). The "Antarctic" and "sulfur" versions of LMD-ZT ("Laboratoire de Météorologie Dynamique - Zoom Tracers") AGCM have been merged for the study of the sulfur cycle at mid- and high-southern latitudes, with a high resolution in the Antarctic region. A method of "lateral" nudging of the Antarctic atmospheric circulation to analysis from the European Centre for Medium-Range Weather Forecasts (ECMWF) has been specifically developed and applied. First, the model has been evaluated. It correctly represents the seasonal cycle of sulfur species at the observation sites in Antarctica. However, several defects have been identified, discussed, and sometimes addressed through specifie numerical experiments. This has enabled us, in the following work, to critically evaluate the sulfur cycle in Antarctica depicted by model results. The model has been used for three different applications, In the first one, the model, evaluated previously, is run in a direct manner in order to estimate the spatial distribution and the seasonal cycle in central regions, and the annuai budget of sulfur species in Antarctica. The second one is a sensitivity study to the formulation of the oceanic dimethylsulfide (DMS) emissions, which appeared to be a key factor for modelling the sulfur cycle. For the third one, the adjoint of the transport model (that enables, in first approach, to go back in time), completed by the adjoint of the chemical module specifically developed for this work, has been used to infer a quantitative assessment of the geographic origin and age of sulfur species in Antarctica.
Cycle du soufre des moyennes et hautes latitudes Sud dans un modèle de circulation générale atmosphérique