Wind forcing effects on coastal circulation and eddy formation around a cape

Abstract. This numerical study aims to assess the role of the wind stress and its resolution on the coastal circulation around the Promontorio of Portofino, a blunt cape in the Ligurian Sea (Northwestern Mediterranean). A high-resolution hydrodynamical numerical model, forced at the inflow open boundary by a coarser regional model, is run in three different configurations: no wind, 21-km and 7-km resolution winds. Moreover, the effect of using different values for the drag coefficient in the wind stress formulation is also tested. Sensitivity analysis of the mass transport and of the current velocity highlights that the greater effect of the wind is near the coast and the higher resolution wind forcing increases the intensity of a coastal countercurrent and of an eddy in the lee of the cape. A cluster analysis is performed to distinguish the main wind patterns and the main coastal flow patterns in the area under study for 2001–2003. It is shown that the typical wind regimes are coherent with the current ones highlighting the key role played by the wind in enhancing the coastal dynamics and the eddy formation around the cape.