A NUMERICAL STUDY OF THE FORMATION OF THE RHONE RIVER PLUME

A three-dimensional primitive equation ocean model is applied to the R hone River plume (northwestern Mediterranean). The plume dynamics are analyzed through the vorticity balance of the depth-averaged current. This balance highlights the importance of the JEBAR and nonlinear term s. The topography induces the freshwaters to enter the Gulf of Fos and progress eastwards. The momentum advection is responsible for the lar ge offshore extension of the plume. Northwestern winds (characteristic of the regional climate) may detach the plume from the coast. The win d stress magnitude required for this detachment is commensurate with G arvine's dimensional analysis. A satisfactory comparison is made betwe en the numerical experiments and satellite observations for weak and s trong wind conditions. Finally, a sensitivity test of the model to the vertical coordinate reveals that a double-sigma system preserves the salinity gradients and current intensity in the frontal zones of the p lume better than a conventional sigma coordinate. (C) 1998 Elsevier Sc ience B.V.