Frequency‐wavenumber spectrum of wind‐generated gravity‐capillary waves

Spatial‐temporal information on wind‐generated gravity‐capillary waves is obtained using a scanning laser slope gauge in a wind wave flume. The results show that a significant portion of short wind wave energy may be contained in wave modes that propagate with the dominant waves rather than at their phase speeds predicted by the dispersion relation. Double‐peaked directional spreading of the spectrum is observed in a certain range of wavenumber and wind stress. A close examination of such results suggests that nonlinear interactions may take place between short waves and higher harmonics of dominant waves or among short waves and enhance the growth of short waves in oblique directions.