ON THE RELATIONSHIP BETWEEN GEOSTROPHIC AND SURFACE WIND AT SEA

Authors:
  • LHLutz Hasse
    Lutz Hasse
  • VWVolker Wagner
    Volker Wagner
  • AGAuthors:LUTZ HASSE1xSearch for articles by this authorAffiliationsDepartment of Oceanography, Oregon State University, Corvallis, Oreg.VOLKER WAGNERxSearch for articles by this authorAffiliationsMeteorologisches Institut der Universität Hamburg, Germany
    Authors:LUTZ HASSE1xSearch for articles by this authorAffiliationsDepartment of Oceanography, Oregon State University, Corvallis, Oreg.VOLKER WAGNERxSearch for articles by this authorAffiliationsMeteorologisches Institut der Universität Hamburg, Germany
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Abstract
The ratio between observed surface and geostrophic wind speed has been investigated from observations at the German Bight, taking geostrophic wind and the air-sea temperature difference as parameters. The ratio decreases with increasing geostrophic wind and increasing stability. While stability is an important parameter for light to moderate winds, variation of the ratio with geostrophic wind speed cannot be neglected, taking the full range of geostrophic wind speeds into consideration. From the Navier-Stokes equations, such a variation is to be expected. For light winds, the (local) surface wind may exceed the (mesoscale) geostrophic wind. Both effects together can be described approximately by a linear relation between the surface wind and geostrophic wind, with a slope of 0.56 and a constant term b>0 varying with stability. The residual error was 2 m/s. Variation with latitude is inferred from the Navier-Stokes equations.