Evaluation of the wave conditions in Madeira Archipelago with spectral models

Abstract

A wave prediction system was implemented and tested in Madeira Archipelago. It is based on two state-of-the-art spectral phase averaging wave models, WAM and SWAN. Ocean-scale simulations, covering almost the entire North Atlantic basin with WAM, provide the boundary conditions for the archipelago. Three levels of SWAN simulations were successively connected to the generation area. For the first level spherical coordinates were still maintained whereas, in order to account better for some coastal processes, the simulations in the second and third levels were performed using the Cartesian coordinates. For the last two computational levels a detailed spatial analysis was carried out. This was focused on the effects of diffraction and triad nonlinear interactions emphasizing the influences induced in the model results when increasing the spatial resolution. The first targets of the analysis were the most energetic cases but, as a further step, wave patterns corresponding to average energetic conditions were also discussed. Two buoys located south of Madeira Island were considered to validate the model system for two winter periods (1997–1998 and 2000–2001) giving a total of about 8 months of simulations. In terms of significant wave heights the system is able to provide accurate results while for the mean periods and directions, the predictions still follow the main wave patterns although the agreement is of lower quality. Comparisons with the results provided by a similar scheme in the Portuguese continental nearshore have been also performed.