SENSITIVITY OF A WAVE MODEL TO WIND VARIABILITY

A third-generation wave model was applied to the Gulf of California to hindcast wave spectra and to assess model sensitivity to wind variabi lity on the basis of three different numerical simulations: (1) when a synthetic wind field of varying randomness is adopted and when the fo rcing wind field considered has an input time step of (2) 6 hours and (3) 5 min. In the first idealized simulation the wave field induced by a constant wind field is compared with the result when white noise wa s added to;the originally constant forcing winds. Results from these n umerical simulations demonstrate that wave energy increases with wind variability, even though the mean wind is kept constant. In the second and third simulations the forcing wind is averaged for periods of 6 h ours and 5 min, which represent relatively low and high timescale vari ability, respectively. These realistic wind fields were constructed as a blend of detailed in situ measurements and analysis information, re presenting wind variability in both speed and direction. The results s how that high-variability winds induce broad directional wave spectra and secondary peaks with similar magnitude as the main peak (bimodal s pectra). With the presence of wind gustiness and a continuous spectrum of wind variability, all source terms are expected to play a signific ant role in the evolution of the wave spectrum.