Wind Input, Surface Dissipation and Directional Properties of Shoaling Waves

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Abstract : This project is a component of the multi-investigator, multi-institutional field study of shoaling surface waves, SHOWEX. The long-term goal of this program is to better understand the dynamics of wave evolution on the shelf, and to improve our predictive modeling capability. My component is closely integrated with another effort of the same name by a group at the University of Miami. The main SHOWEX experiment is scheduled for the fall of 1999 at Duck, North Carolina. Spectral wave models typically describe the evolution of wave energy or action as a function of fetch and duration. The rate of change of energy in each spectral band is the residual of the sum of various source terms that describe the rate of energy input from the wind, the transfer of energy across the wavenumber spectrum due to nonlinear interaction with other wave components, and dissipation (due both to wave breaking and to the drag exerted by the bottom). The data obtained in SHOWEX will be used to establish the evolution of the energy balance in the wave field from the shelf break to the nearshore region. Measurements of wave height and direction, as well as meteorological forcing, and the near-surface rate of turbulent energy dissipation will be obtained from an array of three ASIS (Air-Sea Interaction Spar) buoys, and a SWATH (Small Waterplane Area Twin Hull) ship. Other investigators are responsible for measuring wave dissipation via breaking and bottom friction, as well as providing additional measurements of wave evolution. The component reported here is responsible for near-surface turbulence measurements from the ASIS buoys and the SWATH ship, and for ADCP (Acoustic Doppler Current Profiler) current profiling in the vicinity of one of the buoys.