Dresden 2011 – scientific programme

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UP: Fachverband Umweltphysik

UP 1: Poster Session

UP 1.30: Poster

Tuesday, March 15, 2011, 18:30–20:30, P2

Measurement of Ocean Wave Statistics with the Reflective Stereo Slope Gauge — •Daniel Kiefhaber, Roland Rocholz, Günther Balschbach, and Bernd Jähne — Institut für Umweltphysik, Universität Heidelberg, Deutschland

An optical instrument for the measurement of surface ocean small-scale wave statistics has been developed. This reflective stereo slope gauge (RSSG) is a significant technical improvement of the early work by Waas and Jähne (1992) and capable of simultaneous measurements of height and slope statistics of the water surface in the field. It comprises a stereo camera setup to measure wave heights by stereo triangulation. The slope measurement is based on Cox & Munk’s derivation of slope statistics from photographs of sun glitter (1954) but uses artificial light sources to be independent of natural illumination. The probability distribution of the occurrence of specular reflections in the images can be related to the probability distribution of the surface slope. Although the instrument only makes statistical measurements, it has significant advantages over other common techniques. Measurements are non-invasive (no instrument parts suspended into or submersed in water) and mostly independent of natural illumination (IR light source with λ = 940 nm, IR filters suppress skylight, only direct sun glitter may cause complications), not influenced by upwelling light (strong absorption of light at 940 nm in water) and have a spatial resolution that allows the measurement of slope statistics also for capillary waves. First results from field experiments in the Baltic Sea that demonstrate the RSSG’s capabilities are presented.