Articles | Volume 13, issue 3
Nonlin. Processes Geophys., 13, 265–273, 2006
https://doi.org/10.5194/npg-13-265-2006
Nonlin. Processes Geophys., 13, 265–273, 2006
https://doi.org/10.5194/npg-13-265-2006

  06 Jul 2006

06 Jul 2006

Internal-wave reflection from uniform slopes: higher harmonics and Coriolis effects

T. Gerkema T. Gerkema
  • Royal Netherlands Institute for Sea Research, P.O. Box 59, 1790 AB Den Burg, The Netherlands

Abstract. Weakly nonlinear reflection of internal waves from uniform slopes produces higher harmonics and mean fields; the expressions are here derived for constant stratification and with Coriolis effects fully included, i.e. the horizontal component $\tilde{f}$ of the earth rotation vector (referred to as "non-traditional'') is taken into account. Uniformity in one of the horizontal directions is assumed. It is shown that solutions can be as readily derived with as without $\tilde{f}$; hence there is no need to make the so-called Traditional Approximation. Examples of reflecting internal-wave beams are presented for super-inertial, inertial and sub-inertial frequencies. The problem of resonant and non-resonant forcing of the second harmonic is studied for single plane waves; unlike under the Traditional Approximation, the problem of reflection from a horizontal bottom no longer forms a singular case. Non-traditional effects are favourable to resonant forcing at near-tidal rather than near-inertial frequencies, and generally increase the intensity of the second harmonic. Strong stratification tends to suppress non-traditional effects, but a near-total suppression is only attained for high values of stratification that are characteristic of the seasonal thermocline; in most parts of the ocean, non-traditional effects can therefore be expected to be important.

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