Measurement of Capillary Oscillations of the Sea Surface

Capillary waves on the sea surface have a significant effect on the scattering of both optical and microwave radiation. Although the amplitude of capillary waves is fractions of a millimeter, the slopes formed on capillary waves often exceed 30°, which leads to a strong change in the effective reflection, absorption, and backscattering cross sections. Capillary waves are studied in detail in pools; however, in natural marine conditions, they could only be measured indirectly, usually by reflections or glare. In this paper, a remote method for measuring slopes, amplitudes, and direction of the wave vector of the capillary wave structure in natural conditions is proposed and applied. In the proposed method, distortions of laser beams falling from top to bottom on the sea surface are recorded on a video camera. The authors managed to solve the inverse problem of calculating all the parameters of a capillary wave based on the shape of a capillary comb in video frames. The sensitivity of the method for measuring the wave amplitude is 30 μm at a distance to the surface of over 4 m.