Sensitivity study of wind forcing in a numerical model of mesoscale eddies in the lee of Hawaii islands

Abstract

Abstract. The oceanic circulation around the Hawaiian archipelago is characterized by a complex circulation and the presence of mesoscale eddies west of the islands. These eddies typically develop and persist for weeks to several months in the area during persistent trade wind conditions. In order to find the best setup of a regional ocean model and to better understand the role of the wind forcing in the eddy formation, we compare numerical results obtained using two different wind stress databases: COADS and QuikSCAT. A detailed comparative analysis of wind forcing, modeled kinetic energy and eddy generation is proposed. Moreover, numerical cyclonic eddies are compared with the ones observed during the cruises E-FLUX (Dickey et al., 2008). The main features of the ocean circulation in the area are well reproduced by our model forced by both COADS and QuickSCAT climatologies. Nevertheless, significant differences appear in the levels of kinetic energy and vorticity. The wind-forcing spatial resolution clearly affects the way in which the wind momentum feeds the mesoscale phenomena, and, the higher the resolution, the more realistic the ocean circulation. In particular, the simulation forced by QuikSCAT wind data reproduces well the observed energetic mesoscale structures and their hydrological characteristics and behavior.