On the Probability and Spatial Distribution of Ocean Surface Currents

Yosef Ashkenazy Solar Energy and Environmental Physics, BIDR, Ben-Gurion University, Midreshet Ben-Gurion, Israel

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Hezi Gildor The Fredy and Nadine Herrmann Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel

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Abstract

Insights into the probability distribution of ocean currents are important for various applications such as the chance to encounter extreme events, which may affect, for example, marine construction, and for estimating the energy that can be extracted from the ocean. In addition, for devising better parameterizations for submesoscale mixing, which present climate models cannot resolve, one should understand the velocity distribution and its relation to the various forcing of surface ocean circulation. Here, the authors investigate the probability distribution of surface currents from the Gulf of Eilat/Aqaba measured by high-frequency radar. Their results show that the distribution of ocean current speeds can be approximated by a Weibull distribution. Moreover, the authors demonstrate the existence of spatial variations of the scale and shape parameters of the Weibull distribution over a relatively small region of only a few kilometers. They use a simple surface Ekman layer model to investigate this spatial variability. They find that, when forced by local winds, this model does not reproduce the observations. The addition of Gaussian noise to the zonal and meridional components of the bottom geostrophic currents has only a slight effect on the surface current distribution. However, noise added to the components of the local wind (mimicking wind gusts) has a much greater effect on the distribution of surface currents, suggesting that wind spatial and temporal variability underlay the observed spatial variability of the parameters of the Weibull distribution.

Corresponding author address: Yosef Ashkenazy, Solar Energy and Environmental Physics, BIDR, Ben-Gurion University, Midreshet Ben-Gurion, Israel. E-mail: ashkenaz@bgu.ac.il

Abstract

Insights into the probability distribution of ocean currents are important for various applications such as the chance to encounter extreme events, which may affect, for example, marine construction, and for estimating the energy that can be extracted from the ocean. In addition, for devising better parameterizations for submesoscale mixing, which present climate models cannot resolve, one should understand the velocity distribution and its relation to the various forcing of surface ocean circulation. Here, the authors investigate the probability distribution of surface currents from the Gulf of Eilat/Aqaba measured by high-frequency radar. Their results show that the distribution of ocean current speeds can be approximated by a Weibull distribution. Moreover, the authors demonstrate the existence of spatial variations of the scale and shape parameters of the Weibull distribution over a relatively small region of only a few kilometers. They use a simple surface Ekman layer model to investigate this spatial variability. They find that, when forced by local winds, this model does not reproduce the observations. The addition of Gaussian noise to the zonal and meridional components of the bottom geostrophic currents has only a slight effect on the surface current distribution. However, noise added to the components of the local wind (mimicking wind gusts) has a much greater effect on the distribution of surface currents, suggesting that wind spatial and temporal variability underlay the observed spatial variability of the parameters of the Weibull distribution.

Corresponding author address: Yosef Ashkenazy, Solar Energy and Environmental Physics, BIDR, Ben-Gurion University, Midreshet Ben-Gurion, Israel. E-mail: ashkenaz@bgu.ac.il
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  • Ashkenazy, Y., and H. Gildor, 2009: Long-range temporal correlations of ocean surface currents. J. Geophys. Res., 114, C09009, doi:10.1029/2008JC005235.

    • Search Google Scholar
    • Export Citation
  • Barrick, D. E., B. J. Lipa, and R. D. Crissman, 1985: Mapping surface currents with CODAR. Sea Technol., 26, 4348.

  • Berman, T., N. Paldor, and S. Brenner, 2003: The seasonality of tidal circulation in the Gulf of Elat. Isr. J. Earth Sci., 52, 1119.

  • Biton, E., and H. Gildor, 2011a: The general circulation of the Gulf of Eilat/Aqaba revisited: The interplay between the exchange flow through the Straits of Tiran and surface fluxes. J. Geophys. Res., 116, C08020, doi:10.1029/2010JC006860.

    • Search Google Scholar
    • Export Citation
  • Biton, E., and H. Gildor, 2011b: Stepwise seasonal restratification and the evolution of salinity minimum in the Gulf of Eilat/Aqaba. J. Geophys. Res., 116, C08022, doi:10.1029/2011JC007106.

    • Search Google Scholar
    • Export Citation
  • Biton, E., J. Silverman, and H. Gildor, 2008: Observations and modeling of a pulsating density current. Geophys. Res. Lett., 35, L14603, doi:10.1029/2008GL034123.

    • Search Google Scholar
    • Export Citation
  • Bracco, A., E. P. Chassignet, Z. D. Garraffo, and A. Provenzale, 2003: Lagrangian velocity distributions in a high-resolution numerical simulation of the North Atlantic. J. Atmos. Oceanic Technol., 20, 12121220.

    • Search Google Scholar
    • Export Citation
  • Chu, P. C., 2008: Probability distribution function of the upper equatorial Pacific current speeds. Geophys. Res. Lett., 35, L12606, doi:10.1029/2008GL033669.

    • Search Google Scholar
    • Export Citation
  • Chu, P. C., 2009: Statistical characteristics of the global surface current speeds obtained from satellite altimetry and scatterometer data. IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens., 2, 2732.

    • Search Google Scholar
    • Export Citation
  • Ekman, V. W., 1905: On the influence of the earth’s rotation on ocean-currents. Arch. Math. Astron. Phys., 2, 152.

  • Genin, A., 2008: The physical setting of the Gulf of Aqaba: An explanation for a unique occurrence of tropical communities in the subtropics. Aqaba-Eilat, the Improbable Gulf: Environment, Biodiversity and Preservation, F. D. Por, Ed., Magnes Press, 15–20.

    • Search Google Scholar
    • Export Citation
  • Genin, A., and N. Paldor, 1998: Changes in the circulation and current spectrum near the tip of the narrow, seasonally mixed Gulf of Elat. Isr. J. Earth Sci., 47, 8792.

    • Search Google Scholar
    • Export Citation
  • Genin, A., B. Lazar, and S. Brenner, 1995: Vertical mixing and coral death in the Red Sea following the eruption of Mount Pinatubo. Nature, 377, 507510.

    • Search Google Scholar
    • Export Citation
  • Gildor, H., E. Fredj, J. Steinbuck, and S. Monismith, 2009: Evidence for submesoscale barriers to horizontal mixing in the ocean from current measurements and aerial photographs. J. Phys. Oceanogr., 39, 19751983.

    • Search Google Scholar
    • Export Citation
  • Gildor, H., E. Fredj, and A. Kostinski, 2010: The Gulf of Eilat/Aqaba: A natural driven cavity? Geophys. Astrophys. Fluid Dyn., 104, 301308.

    • Search Google Scholar
    • Export Citation
  • Gill, A. E., 1982: Atmosphere–Ocean Dynamics. Academic Press, 662 pp.

  • Gille, S. T., and S. G. L. Smith, 1998: Probability density functions of large-scale turbulence in the ocean. Phys. Rev. Lett., 81, 52495252.

    • Search Google Scholar
    • Export Citation
  • Gille, S. T., and S. G. L. Smith, 2000: Velocity probability density functions from altimetry. J. Phys. Oceanogr., 30, 125136.

  • Gurgel, K. W., G. Antonischki, H. H. Essen, and T. Schlick, 1999a: Wellen Radar (WERA): A new ground-wave HF radar for ocean remote sensing. Coastal Eng., 37 (3–4), 219234.

    • Search Google Scholar
    • Export Citation
  • Gurgel, K. W., H. H. Essen, and S. P. Kingsley, 1999b: High-frequency radars: Physical limitations and recent developments. Coastal Eng., 37 (3–4), 201218.

    • Search Google Scholar
    • Export Citation
  • Hodgins, D. O., 1994: Remote sensing of ocean surface currents with the Seasonde HF radar. Spill Sci. Technol. Bull., 1, 109129.

  • Kim, S. Y., and Coauthors, 2011: Mapping the U.S. West Coast surface circulation: A multiyear analysis of high-frequency radar observations. J. Geophys. Res., 116, C03011, doi:10.1029/2010JC006669.

    • Search Google Scholar
    • Export Citation
  • Laws, K., J. D. Paduan, and J. Vesecky, 2010: Estimation and assessment of errors related to antenna pattern distortion in CODAR SeaSonde high-frequency radar ocean current measurements. J. Atmos. Oceanic Technol., 27, 10291043.

    • Search Google Scholar
    • Export Citation
  • Lekien, F., and H. Gildor, 2009: Computation and approximation of the length scales of harmonic modes with application to the mapping of surface currents in the Gulf of Eilat. J. Geophys. Res., 114, C06024, doi:10.1029/2008JC004742.

    • Search Google Scholar
    • Export Citation
  • Lekien, F., C. Coulliette, R. Bank, and J. Marsden, 2004: Open-boundary modal analysis: Interpolation, extrapolation, and filtering. J. Geophys. Res., 109, C12004, doi:10.1029/2004JC002323.

    • Search Google Scholar
    • Export Citation
  • Manasrah, R. S., F. A. Al-Horani, M. Y. Rasheed, S. A. Al-Rousan, and M. A. Khalaf, 2006: Patterns of summer vertical and horizontal currents in coastal waters of the northern Gulf of Aqaba, Red Sea. Estuarine Coastal Shelf Sci., 69 (3–4), 567579.

    • Search Google Scholar
    • Export Citation
  • Monahan, A. H., 2006: The probability distribution of sea surface wind speeds. Part I: Theory and SeaWinds observations. J. Climate, 19, 497520.

    • Search Google Scholar
    • Export Citation
  • Monahan, A. H., 2010: The probability distribution of sea surface wind speeds: Effects of variable surface stratification and boundary layer thickness. J. Climate, 23, 51515162.

    • Search Google Scholar
    • Export Citation
  • Monismith, S. G., and A. Genin, 2004: Tides and sea level in the Gulf of Aqaba (Eilat). J. Geophys. Res., 109, C04015, doi:10.1029/2003JC002069.

    • Search Google Scholar
    • Export Citation
  • Saaroni, H., E. Maza, and B. Ziv, 2004: Summer sea breeze, under suppressive synoptic forcing, in a hyper-arid city: Eilat, Israel. Climate Res., 26, 213220.

    • Search Google Scholar
    • Export Citation
  • Seguro, J. V., and T. W. Lambert, 2000: Modern estimation of the parameters of the Weibull wind speed distribution for wind energy analysis. J. Wind Eng. Ind. Aerodyn., 85, 7584.

    • Search Google Scholar
    • Export Citation
  • Wolf-Vecht, A., N. Paldor, and S. Brenner, 1992: Hydrographic indications of the advection/convection effects in the Gulf of Eilat. Deep-Sea Res., 39 (7–8), 13931401.

    • Search Google Scholar
    • Export Citation
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