Surface current effects on the fetch-limited growth of wave energy

To study the fetch-limited growth of wind wave energy over a region with significant lateral shear of the current field, this study exploited data obtained from two linear phased-array High Frequency (HF) radar systems. Both the near-surface currents and wave energy and period were mapped over the highly sheared inshore boundary of the Florida Current. The wave energy growth during two periods when the winds were steady for >12 hours and were directed offshore was computed over a range of fetches from 5 to 45 km. The observed energy growth rates were significantly (similar to 50%) lower than predicted by the Donelan et al. (1992) empirical formulation over the high vorticity region. The reduced growth rate was consistent with a shift of the wind stress direction into the current direction due to refraction of the wave field. Dimensionless wave energy increased by as much as 100% over neighboring values when the vertical component of the surface current vorticity was a global minimum. While trapping and enhancement of wave energy is predicted by wave ray theory, it has never before been confirmed within the Florida Current with coincident wave and current measurements.