Instrument development for combined height/slope/curvature statistics measurements of wind water waves in the field

An optical method for the measurement of slope statistics of capillary and short gravity wind waves on the ocean is currently under development. Specular reflections from infrared LED light sources are observed on the water surface with a stereo camera setup. The principle is similar to Cox & Munk's derivation of slope statistics from photographs of the Sun's glitter. Fractional area of the speckles in the image is related to the local slope probability distribution, speckle size and brightness is correlated with surface curvature, and the local water height can be inferred from parallax in the stereo images. The instrument measures slope statistics locally, making it a beneficial appendix to air-sea interaction measurements. It is scheduled to accompany heat transfer experiments in the Baltic Sea in phase II of the SOPRAN project.