• Apel, J. R., 1994: An improved model of the ocean surface-wave vector spectrum and its effects on radar backscatter. J. Geophys. Res, 99 , 1626916291.

    • Search Google Scholar
    • Export Citation
  • Banner, M. L., 1990: Equilibrium spectra of wind waves. J. Phys. Oceanogr, 20 , 966984.

  • Banner, M. L., I. S. F. Jones, and J. C. Trinder, 1989: Wavenumber spectra of short gravity-waves. J. Fluid Mech, 198 , 321344.

  • Barrick, J., 1968a: A new model for sea clutter. IEEE Trans. Antennas Propag, 16 , 217223.

  • Barrick, J., 1968b: Rough surface scattering based on the specular point theory. IEEE Trans. Antennas Propag, 16 , 449454.

  • Barrick, J., 1974: Wind dependence of quasi-specular microwave sea scatter. IEEE Trans. Antennas Propag, 22 , 135136.

  • Bass, F., M. Fuks, A. Kalmykov, I. Ostrovsky, and A. Rosenberg, 1968: Very high frequency radiowave scattering by a disturbed sea surface. 2. Scattering from an actual sea surface. IEEE Trans. Antennas Propag, 16 , 560568.

    • Search Google Scholar
    • Export Citation
  • Chapron, B., and D. Vandemark, 1996: Analysis of microwave radar cross section at low incidence. The Air–Sea Interface: Radio and Acoustic Sensing, Turbulence and Wave Dynamics, M. Donelan et al., Eds., Vol. 127, The University of Toronto Press, 128–132.

    • Search Google Scholar
    • Export Citation
  • Chapron, B., V. Kerbaol, D. Vandemark, and T. Elfouhaily, 2000: Importance of peakedness in sea surface slope measurements and applications. J. Geophys. Res, 105 , 1719517202.

    • Search Google Scholar
    • Export Citation
  • Chen, W., M. L. Banner, E. J. Walsh, J. B. Jensen, and S. H. Lee, 2001: The southern ocean waves experiment. Part II: Sea surface response to wind speed and wind stress variations. J. Phys. Oceanogr, 31 , 174198.

    • Search Google Scholar
    • Export Citation
  • Chu, J. S., S. R. Long, and O. M. Phillips, 1992: Measurements of the interaction of wave groups with shorter wind-generated waves. J. Fluid Mech, 245 , 191210.

    • Search Google Scholar
    • Export Citation
  • Cox, C., and W. Munk, 1956: Slopes of the sea surface deduced from photographs of sun glitter. Bull. Scripps Inst. Oceanogr, 6 , 401488.

    • Search Google Scholar
    • Export Citation
  • Donelan, M. A., 1974: Generalized profiles of wind speed, temperature and humidity. 17th Conf. on Great Lakes Research, Ann Arbor, MI, International Association of Great Lakes Research, 369–388.

    • Search Google Scholar
    • Export Citation
  • Donelan, M. A., 1987: The effect of swell on the growth of wind waves. APL Tech. Dig, 8 , 1823.

  • Dyer, A., 1974: A review of flux-profile relationships. Bound.-Layer Meteor, 7 , 363372.

  • 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 , 1578115796.

    • Search Google Scholar
    • Export Citation
  • Elfouhaily, T., D. Vandemark, J. Gourrion, and B. Capron, 1998: Estimation of wind stress using dual-frequency Topex data. J. Geophys. Res, 103 , 2510125108.

    • Search Google Scholar
    • Export Citation
  • Fairall, C. W., E. F. Bradley, D. P. Rogers, J. B. Edson, and G. S. Young, 1996: Bulk parameterization of air–sea fluxes for Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment. J. Geophys. Res, 101 , 37473764.

    • Search Google Scholar
    • Export Citation
  • French, J., G. Crescenti, T. Crawford, and E. J. Dumas, 2000: Longez (N3R) participation in the 1999 Shoaling Waves Experiment (SHOWEX). NOAA Data Rep. OAR ARL-20, 51 pp.

    • Search Google Scholar
    • Export Citation
  • Glazman, R. E., and A. Greysukh, 1993: Satellite altimeter measurements of surface wind. J. Geophys. Res, 98 , 24752483.

  • Gommenginger, C. P., M. A. Srokosz, P. G. Challenor, and P. D. Cotton, 2002: Development and validation of altimeter wind speed algorithms using an extended collocated buoy/Topex dataset. IEEE Trans. Geosci. Remote Sens, 40 , 251260.

    • Search Google Scholar
    • Export Citation
  • Gotwols, B. L., and D. R. Thompson, 1994: Ocean microwave backscatter distributions. J. Geophys. Res, 99 , 97419750.

  • Gourrion, J., D. Vandemark, S. Bailey, and B. Chapron, 2002a: Investigation of C-band altimeter cross section dependence on wind speed and sea state. Can. J. Remote Sens, 28 , 484489.

    • Search Google Scholar
    • Export Citation
  • Gourrion, J., D. Vandemark, S. Bailey, B. Chapron, G. P. Gommenginger, P. G. Challenor, and M. A. Srokosz, 2002b: A two-parameter wind speed algorithm for Ku-band altimeters. J. Atmos. Oceanic Technol, 19 , 20302048.

    • Search Google Scholar
    • Export Citation
  • Graber, H. C., E. A. Terray, M. A. Donelan, W. M. Drennan, and J. C. Van Leer, 2000: ASIS—A new air–sea interaction spar buoy: Design and performance at sea. J. Atmos. Oceanic Technol, 17 , 708720.

    • Search Google Scholar
    • Export Citation
  • Hesany, V., W. J. Plant, and W. C. Keller, 2000: The normalized radar cross section of the sea at 10 degrees incidence. IEEE Trans. Geosci. Remote Sens, 38 , 6472.

    • Search Google Scholar
    • Export Citation
  • Hwang, P. A., and O. H. Shemdin, 1988: The dependence of sea-surface slope on atmospheric stability and swell conditions. J. Geophys. Res, 93 , 1390313912.

    • Search Google Scholar
    • Export Citation
  • Hwang, P. A., S. Atakturk, M. A. Sletten, and D. B. Trizna, 1996: A study of the wavenumber spectra of short water waves in the ocean. J. Phys. Oceanogr, 26 , 12661285.

    • Search Google Scholar
    • Export Citation
  • Hwang, P. A., W. J. Teague, G. A. Jacobs, and D. W. Wang, 1998: A statistical comparison of wind speed, wave height, and wave period derived from satellite altimeters and ocean buoys in the Gulf of Mexico region. J. Geophys. Res, 103 , 1045110468.

    • Search Google Scholar
    • Export Citation
  • Jackson, F. C., W. T. Walton, D. E. Hines, B. A. Walter, and C. Y. Peng, 1992: Sea-surface mean-square slope from Ku-band backscatter data. J. Geophys. Res, 97 , 1141111427.

    • Search Google Scholar
    • Export Citation
  • Liu, Y., X. H. Yan, W. T. Liu, and P. A. Hwang, 1997: The probability density function of ocean surface slopes and its effects on radar backscatter. J. Phys. Oceanogr, 27 , 782797.

    • Search Google Scholar
    • Export Citation
  • Longuet-Higgins, M. S., 1963: The effects of non-linearities on the statistical distribution in the theory of sea waves. J. Fluid Mech, 17 , 459480.

    • Search Google Scholar
    • Export Citation
  • Longuet-Higgins, M. S., 1982: On the skewness of sea surface slopes. J. Phys. Oceanogr, 12 , 12831291.

  • Mahrt, L., D. Vickers, J. L. Sun, T. L. Crawford, G. Crescenti, and P. Frederickson, 2001: Surface stress in offshore flow and quasi-frictional decoupling. J. Geophys. Res, 106 , 2062920639.

    • Search Google Scholar
    • Export Citation
  • Masuko, H., K. I. Okamoto, M. Shimada, and S. Niwa, 1986: Measurement of microwave backscattering signatures of the ocean surface using X-band and Ka-band airborne scatterometers. J. Geophys. Res, 91 , 30653083.

    • Search Google Scholar
    • Export Citation
  • Melville, W. K., and P. Matusov, 2002: Distribution of breaking waves at the ocean surface. Nature, 417 , 5863.

  • Melville, W. K., R. H. Stewart, W. C. Keller, J. A. Kong, D. V. Arnold, A. T. Jessup, M. R. Loewen, and A. M. Slinn, 1991: Measurements of electromagnetic bias in radar altimetry. J. Geophys. Res, 96 , 49154924.

    • Search Google Scholar
    • Export Citation
  • Paulson, C. A., 1970: The mathematical representation of wind speed and temperature profiles in the unstable atmospheric surface layer. J. Appl. Meteor, 9 , 857861.

    • Search Google Scholar
    • Export Citation
  • Phillips, O. M., 1977: The Dynamics of the Upper Ocean. 2d ed. Cambridge University Press, 336 pp.

  • Plant, W. J., 2002: A stochastic, multiscale model of microwave backscatter from the ocean. J. Geophys. Res.,107, 3120, doi:10.1029/ 2000JC000909.

    • Search Google Scholar
    • Export Citation
  • Shaw, J. A., and J. H. Churnside, 1997: Scanning-laser glint measurements of sea-surface slope statistics. Appl. Opt, 36 , 42024213.

  • Stogryn, A., 1997: Equations for the permittivity of sea water. Gencorp Aerojet. Tech. Rep.

  • Sun, J. L., D. Vandemark, L. Mahrt, D. Vickers, T. Crawford, and C. Vogel, 2001: Momentum transfer over the coastal zone. J. Geophys. Res, 106 , 1243712448.

    • Search Google Scholar
    • Export Citation
  • Sverdup, H., and W. Munk, 1947: Wind, sea, and swell: Theory of relations for forecasting. U.S. Hydrographic Office Tech. Rep. 1, 44 pp.

    • Search Google Scholar
    • Export Citation
  • Tatarskii, V. I., 2003: Multi-Gaussian representation for the Cox– Munk distribution of slopes for wind-driven waves. J. Atmos. Oceanic Technol, 20 , 16971705.

    • Search Google Scholar
    • Export Citation
  • Valenzuela, G. R., 1978: Theories for the interaction of electromagnetic and oceanic waves: A review. Bound.-Layer Meteor, 13 , 6185.

  • Vandemark, D., J. B. Edson, and B. Chapron, 1997: Altimeter estimation of sea surface wind stress for light to moderate winds. J. Atmos. Oceanic Technol, 14 , 716722.

    • Search Google Scholar
    • Export Citation
  • Vandemark, D., T. Crawford, R. Dobosy, T. Elfouhaily, and B. Chapron, 1999: Sea surface slope statistics from a low-altitude aircraft. Int. Geosci. Remote Sens. Symp., Vol. 2, Hamburg, Germany, IEEE, 381– 383.

    • Search Google Scholar
    • Export Citation
  • Vandemark, D., P. D. Mourad, S. A. Bailey, T. L. Crawford, C. A. Vogel, J. Sun, and B. Chapron, 2001: Measured changes in ocean surface roughness due to atmospheric boundary layer rolls. J. Geophys. Res, 106 , 46394654.

    • Search Google Scholar
    • Export Citation
  • Vickers, D., L. Mahrt, J. L. Sun, and T. Crawford, 2001: Structure of offshore flow. Mon. Wea. Rev, 129 , 12511258.

  • Walsh, E. J., D. C. Vandemark, C. A. Friehe, S. P. Burns, D. Khelif, R. N. Swift, and J. F. Scott, 1998: Measuring sea surface mean square slope with a 36-GHz scanning radar altimeter. J. Geophys. Res, 103 , 1258712601.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 399 174 12
PDF Downloads 237 105 7

Ocean Wave Slope Observations Using Radar Backscatter and Laser Altimeters

View More View Less
  • 1 NASA Goddard Space Flight Center, Wallops Island, Virginia
  • | 2 Département d'Océanographie Spatiale, IFREMER, Plouzané, France
  • | 3 National Center for Atmospheric Research, Boulder, Colorado
  • | 4 NOAA Field Research Division, Idaho Falls, Idaho
  • | 5 University of Miami, Miami, Florida
Restricted access

Abstract

Combination of laser and radar aboard an aircraft is used to directly measure long gravity wave surface tilting simultaneously with nadir-viewing microwave backscatter from the sea surface. The presented dataset is extensive, encompassing varied wind conditions over coastal and open-ocean wave regimes. Laser-derived slope statistics and Ka-band (36 GHz) radar backscatter are detailed separately to document their respective variations versus near-surface wind speed. The slope statistics, measured for λ > 1–2 m, show good agreement with Cox and Munk's oil-slickened sea measurements. A notable exception is elevated distribution peakedness and an observed wind dependence in this likely proxy for nonlinear wave–wave interactions. Aircraft Ka-band radar data nearly mimic Ku-band satellite altimeter observations in their mean wind dependence. The present calibrated radar data, along with relevant observational and theoretical studies, suggest a large (−5 dB) bias in previous Ka-band results. Next, wave-diverse inland, coastal, and open-ocean observations are contrasted to show wind-independent long-wave slope variance changes of a factor of 2–3, always increasing as one heads to sea. Combined long-wave and radar data demonstrate that this long-wave tilt field variability is largely responsible for radar backscatter variations observed at a given wind speed, particularly at wind speeds below 5–7 m s−1. Results are consistent with, and provide quantititative support for, recent satellite altimeter studies eliciting signatures of long-wave impacts resident in the radar backscatter. Under a quasi-optical scattering assumption, the results illustrate long-wave control on the variance of the total mean square slope parameter due to changes in the directional long-wave spectrum, with high-wavenumbers being relatively unaffected in a mean sense. However, further analysis suggests that for winds above 7 m s−1 the high-wavenumber subrange also varies with change in the longer wave field slope and/or energy, the short gravity wave roughness being measurably greater for smoother seas.

Corresponding author address: Douglas Vandemark, Ocean Process Analysis Laboratory, 39 College Road, 142 Morse Hall, Durham, NH 03824. Email: douglas.vandemark@nasa.gov

Abstract

Combination of laser and radar aboard an aircraft is used to directly measure long gravity wave surface tilting simultaneously with nadir-viewing microwave backscatter from the sea surface. The presented dataset is extensive, encompassing varied wind conditions over coastal and open-ocean wave regimes. Laser-derived slope statistics and Ka-band (36 GHz) radar backscatter are detailed separately to document their respective variations versus near-surface wind speed. The slope statistics, measured for λ > 1–2 m, show good agreement with Cox and Munk's oil-slickened sea measurements. A notable exception is elevated distribution peakedness and an observed wind dependence in this likely proxy for nonlinear wave–wave interactions. Aircraft Ka-band radar data nearly mimic Ku-band satellite altimeter observations in their mean wind dependence. The present calibrated radar data, along with relevant observational and theoretical studies, suggest a large (−5 dB) bias in previous Ka-band results. Next, wave-diverse inland, coastal, and open-ocean observations are contrasted to show wind-independent long-wave slope variance changes of a factor of 2–3, always increasing as one heads to sea. Combined long-wave and radar data demonstrate that this long-wave tilt field variability is largely responsible for radar backscatter variations observed at a given wind speed, particularly at wind speeds below 5–7 m s−1. Results are consistent with, and provide quantititative support for, recent satellite altimeter studies eliciting signatures of long-wave impacts resident in the radar backscatter. Under a quasi-optical scattering assumption, the results illustrate long-wave control on the variance of the total mean square slope parameter due to changes in the directional long-wave spectrum, with high-wavenumbers being relatively unaffected in a mean sense. However, further analysis suggests that for winds above 7 m s−1 the high-wavenumber subrange also varies with change in the longer wave field slope and/or energy, the short gravity wave roughness being measurably greater for smoother seas.

Corresponding author address: Douglas Vandemark, Ocean Process Analysis Laboratory, 39 College Road, 142 Morse Hall, Durham, NH 03824. Email: douglas.vandemark@nasa.gov

Save