A Study of the Wavenumber Spectra of Short Water Waves in the Ocean. Part II: Spectral Model and Mean Square Slope

This paper presents a wavenumber spectral model of the surface water waves in the capillary–gravity regime. The database for the analysis consists of spatial and temporal measurements of surface slopes obtained from a scanning slope sensor buoy operating in free-drift mode in the Atlantic Ocean. These data indicate that the contribution of mean square slopes from capillary–gravity waves (wavelengths from 4 mm to 6 cm) is a significant portion of the total mean square slopes. The resulting mean square slopes derived from the proposed spectral model are in excellent agreement with existing field datasets. The properties of short waves, including the mean square slopes and wind speed dependence of the spectral intensity of individual wave components, derived from optical and microwave sensors are also compared. Significant differences in terms of the magnitudes of the mean square slopes and the exponents of wind speed dependence are found. Some of the possible explanations of the discrepancies are explored.