Observation of Short Wind Waves in Coastal Waters*

Abstract

Observations of wind-generated gravity–capillary waves have been made during two recent field programs in coastal environments. The results of wave slope spectra on clean water show a well-defined correlation with the wind friction velocity. However, spectral values at higher wavenumbers (above 200 rad m−1) are significantly higher than previous laboratory results. In the presence of surface films wave spectra may decrease by more than one order of magnitude at lower wind stresses. The dispersion characteristics of short waves vary markedly depending on the wavenumber, the wind stress, and the surface chemical condition. Some results in the presence of surface films at intermediate winds show much higher apparent phase speeds than the theoretical dispersion relation. This may be because of an enhanced near-surface current or because of the relative increase of wave energy that is phase-locked to longer steep gravity waves.