• Alpers, W., 1985: Theory of radar imaging of internal waves. Nature, 314, 245247, doi:10.1038/314245a0.

  • Alpers, W., and I. Hennings, 1984: A theory of the imaging mechanism of underwater bottom topography by real and synthetic aperture radar. J. Geophys. Res.,89, 10 529–10 546, doi:10.1029/JC089iC06p10529.

  • Apel, J. R., H. M. Byrne, J. R. Proni, and R. L. Charnell, 1975: Observations of oceanic internal and surface waves from the earth resources technology satellite. J. Geophys. Res., 80, 865881, doi:10.1029/JC080i006p00865.

    • Search Google Scholar
    • Export Citation
  • Beal, R. C., P. S. DeLeonibus, and I. Katz, Eds., 1981: Spaceborne Synthetic Aperture Radar for Oceanography.Vol. 7. Johns Hopkins University Press, 215 pp.

  • Beal, R. C., V. N. Kudryavtsev, D. R. Thompson, S. A. Grodsky, D. G. Tilley, V. A. Dulov, and H. C. Graber, 1997: The influence of the marine atmospheric boundary layer on ERS 1 synthetic aperture radar imagery of the Gulf Stream. J. Geophys. Res.,102, 5799–5814, doi:10.1029/96JC03109.

  • Cox, C., and W. Munk, 1954: Measurement of the roughness of the sea surface from photographs of the sun’s glitter. J. Opt. Soc. Amer., 44, 838850, doi:10.1364/JOSA.44.000838.

    • Search Google Scholar
    • Export Citation
  • Donelan, M. A., J. Hamilton, and W. H. Hui, 1985: Directional spectra of wind-generated waves. Philos. Trans. Roy. Soc. London, A315, 509562, doi:10.1098/rsta.1985.0054.

    • Search Google Scholar
    • Export Citation
  • Dulov, V., and V. Kudryavtsev, 1990: Imagery of the inhomogeneities of currents on the ocean surface state. Sov. J. Phys. Oceanogr.,1, 325–336, doi:10.1007/BF02196830.

  • Elfouhaily, T., B. Chapron, K. Katsaros, and D. Vandemark, 1997: A unified directional spectrum for long and short wind-driven waves. J. Geophys. Res., 102, 15 78115 796, doi:10.1029/97JC00467.

    • Search Google Scholar
    • Export Citation
  • Espedal, H. A., O. M. Johannessen, J. A. Johannessen, E. Dano, D. Lyzenga, and J. Knulst, 1998: COASTWATCH’95: ERS 1/2 SAR detection of natural film on the ocean surface. J. Geophys. Res.,103, 24 969–24 982, doi:10.1029/98JC01660.

  • Ferrari, R., 2011: A frontal challenge for climate models. Science, 332, 316317, doi:10.1126/science.1203632.

  • Fox-Kemper, B., and Coauthors, 2011: Parameterization of mixed layer eddies. III: Implementation and impact in global ocean climate simulations. Ocean Modell., 39, 6178, doi:10.1016/j.ocemod.2010.09.002.

    • Search Google Scholar
    • Export Citation
  • Fu, L.-L., and B. Holt, 1983: Some examples of detection of oceanic mesoscale eddies by the SEASAT synthetic-aperture radar. J. Geophys. Res.,88, 1844–1852, doi:10.1029/JC088iC03p01844.

  • Fu, L.-L., D. Alsdorf, R. Morrow, E. Rodriguez, and N. Mognard, 2012: SWOT: The Surface Water and Ocean Topography mission: Wide-swath altimetric measurement of water elevation on Earth. Jet Propulsion Laboratory JPL Publ. 12-5, 228 pp. [Available online at http://hdl.handle.net/2014/41996.]

  • Hua, B. L., 1994: Skewness of the generalized centrifugal force divergence for a joint normal distribution of strain and vorticity components. Phys. Fluids, 6, 3200, doi:10.1063/1.868101.

    • Search Google Scholar
    • Export Citation
  • Hughes, B., 1978: The effect of internal waves on surface wind waves 2. Theoretical analysis. J. Geophys. Res., 83, 455465, doi:10.1029/JC083iC01p00455.

    • Search Google Scholar
    • Export Citation
  • Huot, J., M. Rast, S. Delwart, J. Bezy, G. Levrini, and H. Tait, 2001: The optical imaging instruments and their applications: AATSR and MERIS. ESA Bull., 106, 56–66. [Available online at http://esamultimedia.esa.int/multimedia/publications/ESA-Bulletin-106/.]

    • Search Google Scholar
    • Export Citation
  • Jansen, R. W., C. Y. Shen, S. R. Chubb, A. L. Cooper, and T. Evans, 1998: Subsurface, surface, and radar modeling of a Gulf Stream current convergence. J. Geophys. Res.,103, 18 723–18 743, doi:10.1029/98JC01195.

  • Johannessen, J. A., R. A. Shuchman, G. Digranes, D. Lyzenga, C. Wackerman, O. M. Johannessen, and P. Vachon, 1996: Coastal ocean fronts and eddies imaged with ERS 1 synthetic aperture radar. J. Geophys. Res.,101, 6651–6667, doi:10.1029/95JC02962.

  • Johannessen, J. A., V. Kudryavtsev, D. Akimov, T. Eldevik, N. Winther, and B. Chapron, 2005: On radar imaging of current features: 2. Mesoscale eddy and current front detection. J. Geophys. Res.,110, C07017, doi:10.1029/2004JC002802.

  • Keller, W., and J. Wright, 1975: Microwave scattering and the straining of wind-generated waves. Radio Sci., 10, 139147, doi:10.1029/RS010i002p00139.

    • Search Google Scholar
    • Export Citation
  • Klein, P., B. Hua, G. Lapeyre, X. Capet, S. Le Gentil, and H. Sasaki, 2008: Upper ocean turbulence from high-resolution 3D simulations. J. Phys. Oceanogr., 38, 17481763, doi:10.1175/2007JPO3773.1.

    • Search Google Scholar
    • Export Citation
  • Kudryavtsev, V. N., V. K. Makin, and B. Chapron, 1999: Coupled sea surface-atmosphere model: 2. Spectrum of short wind waves. J. Geophys. Res., 104, 76257639, doi:10.1029/1999JC900005.

    • Search Google Scholar
    • Export Citation
  • Kudryavtsev, V., D. Akimov, J. Johannessen, and B. Chapron, 2005: On radar imaging of current features: 1. Model and comparison with observations. J. Geophys. Res.,110, C07016, doi:10.1029/2004JC002505.

  • Kudryavtsev, V., A. Myasoedov, B. Chapron, J. A. Johannessen, and F. Collard, 2012a: Joint sun-glitter and radar imagery of surface slicks. Remote Sens. Environ., 120, 123132, doi:10.1016/j.rse.2011.06.029.

    • Search Google Scholar
    • Export Citation
  • Kudryavtsev, V., A. Myasoedov, B. Chapron, J. A. Johannessen, and F. Collard, 2012b: Imaging mesoscale upper ocean dynamics using synthetic aperture radar and optical data. J. Geophys. Res.,117, C04029, doi:10.1029/2011JC007492.

  • Kundu, P., 1990: Fluid Mechanics.Academic Press, 638 pp.

  • Lévy, M., R. Ferrari, P. J. Franks, A. P. Martin, and P. Rivière, 2012: Bringing physics to life at the submesoscale. Geophys. Res. Lett., 39, L14602, doi:10.1029/2012GL052756.

    • Search Google Scholar
    • Export Citation
  • McWilliams, J., F. Colas, and M. Molemaker, 2009: Cold filamentary intensification and oceanic surface convergence lines. Geophys. Res. Lett., 36, L18602, doi:10.1029/2009GL039402.

    • Search Google Scholar
    • Export Citation
  • Okubo, A., 1970: Horizontal dispersion of floatable particles in the vicinity of velocity singularities such as convergences. Deep-Sea Res. Oceanogr. Abstr., 17, 445454, doi:10.1016/0011-7471(70)90059-8.

    • Search Google Scholar
    • Export Citation
  • Phillips, O. M., 1958: The equilibrium range in the spectrum of wind-generated waves. J. Fluid Mech., 4, 426433, doi:10.1017/S0022112058000550.

    • Search Google Scholar
    • Export Citation
  • Phillips, O. M., 1984: On the response of short ocean wave components at a fixed wavenumber to ocean current variations. J. Phys. Oceanogr., 14, 14251433, doi:10.1175/1520-0485(1984)014<1425:OTROSO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Plant, W. J., 1982: A relationship between wind stress and wave slope. J. Geophys. Res., 87, 19611967, doi:10.1029/JC087iC03p01961.

  • Yurovskaya, M., V. Dulov, B. Chapron, and V. Kudryavtsev, 2013: Directional short wind wave spectra derived from the sea surface photography. J. Geophys. Res., 118, 43804394, doi:10.1002/jgrc.20296.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 5 5 5
PDF Downloads 3 3 3

Surface Roughness Imaging of Currents Shows Divergence and Strain in the Wind Direction

View More View Less
  • 1 Laboratoire d’Océanographie Spatiale, Institut Francais de Recherche pour l’Exploitation de la Mer, Plouzané, France, and Nansen-Tutu Center, Department of Oceanography, University of Cape Town, Rondebosch, South Africa
  • | 2 Laboratoire d’Océanographie Spatiale, Institut Francais de Recherche pour l’Exploitation de la Mer, Plouzané, France
  • | 3 Laboratoire de Physique des Océans, Institut Francais de Recherche pour l’Exploitation de la Mer, Plouzané, France
  • | 4 Laboratoire d’Océanographie Spatiale, Institut Francais de Recherche pour l’Exploitation de la Mer, Plouzané, France
  • | 5 Laboratoire de Physique des Océans, Institut Francais de Recherche pour l’Exploitation de la Mer, Plouzané, France
Restricted access

Abstract

Images of sea surface roughness—for example, obtained by synthetic aperture radars (SAR) or by radiometers viewing areas in and around the sun glitter—at times provide clear observations of meso- and submesoscale oceanic features. Interacting with the surface wind waves, particular deformation properties of surface currents are responsible for those manifestations. Ignoring other sources of surface roughness variations, the authors limit their discussion to the mean square slope (mss) variability. This study confirms that vortical currents and currents with shear in the wind direction shall not be expressed in surface roughness images. Only divergent currents or currents with no divergence but strained in the wind direction can exhibit surface roughness signatures. More specifically, nondivergent currents might be traced with a 45° sensitivity to the wind direction. A simple method is proposed in order to interpret high-resolution roughness images, where roughness variations are proportional to ∂u/∂x + αυ/∂y, a linear combination of the along-wind and crosswind current gradients. The polarization parameter α depends upon the sensor look direction and the directional properties of the surface waves selected by the sensor. The use of multiple look directions or possible acquisitions with different wind directions shall thus help to retrieve surface currents from surface roughness observations.

Corresponding author address: Nicolas Rascle, Laboratoire d’Océanographie Spatiale, IFREMER, ZI Pointe du Diable, 29280 Plouzané, France. E-mail: nicolas.rascle@ifremer.fr

Abstract

Images of sea surface roughness—for example, obtained by synthetic aperture radars (SAR) or by radiometers viewing areas in and around the sun glitter—at times provide clear observations of meso- and submesoscale oceanic features. Interacting with the surface wind waves, particular deformation properties of surface currents are responsible for those manifestations. Ignoring other sources of surface roughness variations, the authors limit their discussion to the mean square slope (mss) variability. This study confirms that vortical currents and currents with shear in the wind direction shall not be expressed in surface roughness images. Only divergent currents or currents with no divergence but strained in the wind direction can exhibit surface roughness signatures. More specifically, nondivergent currents might be traced with a 45° sensitivity to the wind direction. A simple method is proposed in order to interpret high-resolution roughness images, where roughness variations are proportional to ∂u/∂x + αυ/∂y, a linear combination of the along-wind and crosswind current gradients. The polarization parameter α depends upon the sensor look direction and the directional properties of the surface waves selected by the sensor. The use of multiple look directions or possible acquisitions with different wind directions shall thus help to retrieve surface currents from surface roughness observations.

Corresponding author address: Nicolas Rascle, Laboratoire d’Océanographie Spatiale, IFREMER, ZI Pointe du Diable, 29280 Plouzané, France. E-mail: nicolas.rascle@ifremer.fr
Save