Ocean Surface Wave Optical Roughness: Innovative Polarization Measurement
COLUMBIA UNIV PALISADES NY LAMONT-DOHERTY EARTH OBSERVATORY
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Nonlinear interfacial roughness elements - sharp crested waves, breaking waves as well as the foam, subsurface bubbles and spray they produce, contribute substantially to the distortion of the optical transmission through the air-sea interface. These common surface roughness features occur on a wide range of length scales, from the dominant sea state down to capillary waves. Wave breaking signatures range from large whitecaps with their residual passive foam, down to the ubiquitous centimeter scale microscale breakers that do not entrain air. There is substantial complexity in the local wind-driven sea surface roughness microstructure, as is evident in the close range image shown in Figure 1. Traditional descriptors of sea surface roughness are scale-integrated statistical properties, such as significant wave height, mean squared slope e.g. Cox and Munk, 1954 and breaking probability e.g. Holthuijsen and Herbers, 1986. Subsequently, spectral characterisations of wave height, slope and curvature have been measured, providing a scale resolution into Fourier modes for these geometrical sea roughness parameters. More recently, measurements of whitecap crest length spectral density e.g. Phillips et al, 2001, Gemmrich et al., 2008 and microscale breaker crest length spectral density e.g. Jessup and Phadnis, 2005 have been reported.
- Physical and Dynamic Oceanography