ATMOSPHERIC TRAJECTORY MODELS FOR SIMULATION OF LONG-RANGE TRANSPORT AND DIFFUSION OVER THE WESTERN MEDITERRANEAN

Studies carried out in the Centre d'Estudis Avancats de Blanes about the importance of the atmospheric fluxes of nutrients near the coast indicate that the quantities of nitrate deposited are of the same order of magnitude as the vertical diffusive fluxes from deep waters. Therefore, the atmosphere would be an important source of nutrients for the marine productivity, particularly, in oligotrophic waters constituting the greatest part of the Mediterranean Sea. Implementation of long-range trajectory models has been made in order to simulate transport of pollutants over the Western Mediterranean. Three lagrangian models of increasing complexity have been developed assuming different simplifications to the conservation equations. The first one, a purely kinematic 2-D method uses averaged wind in a layer. It is appropriate for determining the dominant fluxes at a region of interest, considering a large number of trajectories. The second, an isentropic model, computes trajectories following the surfaces of constant potential temperature: Finally, a 3-D model for complex regions, incorporates physical processes such as those induced by orography, flux energy, atmospheric stability and horizontal thermal gradients.