Measurement of wave crest length and groupiness from spaceborne Synthetic Aperture Radar

Most measurements of ocean surface wave variations are made in the temporal domain, i.e wave height or slope as a function of time. By contrast, a synthetic aperture radar (SAR) is capable of measuring waves in the twodimensional spatial domain at essentially a single instant. As a consequence, SAR imagery affords us a unique opportunity to examine some of the non-linear features of ocean surface waves. In this paper, we use spaceborne SAR imagery from the Shuttle Imaging Radar-B (SIR-B) mission to estimate wave crest length and groupiness. These features may contribute to the likelihood of encountering an especially devastating large wave. After providing a specific procedure for objectively computing these quantities, we find that the crest lengths are longer and groupiness more prevalent that one would expect based on linear wave theory.