ON THE WIND-DRIVEN COASTAL UPWELLING IN THE GULF OF LIONS

Satellite imagery has revealed the existence of discrete and relatively cool zones of surface upwelled water along the Mediterranean coast of the Gulf of Lions off the South of France. The imagery relates to a period of time during which the character of the local surface wind field corresponds to the onset and subsequent persistence of a Mistral-Tramontane event, this consisting of strong northerly and northwesterly winds. Using a multi-level three-dimensional numerical model of wind-driven coastal upwelling dynamics in which turbulence closure is achieved at the level of the turbulence energy equation, experiments have been performed with a parameter setting appropriate to the onset of a Mistral-Tramontane event in the Gulf of Lions. Good agreement is obtained between the predicted zones of coastal upwelling (characterized by local reductions in sea-surface temperature) and the results of the satellite thermal imagery. In process-orientated evaluations, an account is given of the depth-structure of the momentum and thermal fields supporting the coastal upwelling.