Focusing of an inertia - gravity wave packet by a baroclinic shear flow

Edwards, N. R. and Staquet, C. (2005). Focusing of an inertia - gravity wave packet by a baroclinic shear flow. Dynamics of Atmospheres and Oceans, 40(1-2) pp. 91–113.



We investigate the interaction of a small-amplitude internal gravity wave packet in a rotating fluid with a baroclinic shear flow. Ray equations and three-dimensional direct numerical simulations of the Boussinesq equations are solved for this purpose. The shear flow has a simple structure and depends separately on the vertical and horizontal coordinates. We focus on the situation where the intrinsic frequency Ω of the wave packet increases as the packet propagates into the shear flow, due to the horizontal dependence of this flow. The packet is trapped in the neighbourhood of the Ω=N surface (where N is the spatially varying Brunt-Väisälä frequency) and the wave-induced velocity, which first decays because of dispersion, is amplified there. The ray equations show that the packet may undergo multiple reflections within a wave guide formed by sections of the Ω=N surface, and thus penetrate into the shear flow. Three-dimensional numerical simulations of the same problem show that most of the wave packet is actually dissipated once trapped because both the group velocity and the horizontal scale of the packet have strongly decreased through the interaction. Consequently, the wave packet is not able to travel across the shear flow, except when the latter vanishes locally.

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  • Item ORO ID
  • 25682
  • Item Type
  • Journal Item
  • ISSN
  • 0377-0265
  • Extra Information
  • NOTICE: this is the author’s version of a work that was accepted for publication in Dynamics of Atmospheres and Oceans. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published as cited above
  • Keywords
  • baroclinic shear flow; inertia–gravity wave packet; ray tracing; direct numerical simulations
  • Academic Unit or School
  • Faculty of Science, Technology, Engineering and Mathematics (STEM) > Environment, Earth and Ecosystem Sciences
    Faculty of Science, Technology, Engineering and Mathematics (STEM)
  • Copyright Holders
  • © 2004 Elsevier B. V.
  • Depositing User
  • Neil Edwards