The properties of high frequency capillary waves generated by steep gravity waves on deep water have been measured with a high resolution laser optical slope gauge. The results have been compared with the steady theory of Longuet-Higgins (1963). Good qualitative agreement is obtained. However, the quantitative predictions of the capillary wave slopes cannot be verified by the data because the theory requires knowledge of an idealized quantity - the crest curvature of the gravity wave in the absence of surface tension - which cannot be measured experimentally.

The magnitudes of water surface temperature fluctuations induced by surface waves of known dynamic characteristics were measured. An infrared radiometer, capable of detecting temperature changes less than 10−4 °C with response only in the 8‐ to 13‐μm spectral region, was the prime diagnostic tool. The major experimental task was to discriminate between the thermal and reflectance contributions to the wave‐induced total radiometric signal. A technique which measures the upper bound of the reflectance contribution was developed, validated, and implemented. The magnitude of the measured temperature fluctuations induced by small amplitude monochromatic surface waves of near‐ideal characteristics agreed well with predictions from linear theories. In the linear wave dynamic regime the amplitude of the wave‐induced temperature fluctuation is dependent upon the near‐surface heat transfer. This dependence was found to be linear by systematically increasing the surface heat transfer by means of an increase in wind velocity.

In this paper, we describe TRW's latest version of the scanning laser slope gauge (SLSG) which was used to characterize the sea surface in a recent ocean experiment. The SLSG, capable of measuring the spatial distribution and temporal evolution of the surface slopes of a patch of ocean, provides ground truth data which form a quantitative basis for the understanding of ocean wind-wave interactions and the development and validation of radar scattering models relevant to ocean remote sensing.