Preprints
https://doi.org/10.5194/osd-11-753-2014
https://doi.org/10.5194/osd-11-753-2014

  05 Mar 2014

05 Mar 2014

Review status: this preprint was under review for the journal OS but the revision was not accepted.

Dynamics of turbulent western boundary currents at low latitude in a shallow water model

C. Q. C. Akuetevi1,2 and A. Wirth1 C. Q. C. Akuetevi and A. Wirth
  • 1Univ. Grenoble Alpes, CNRS, LEGI UMR5519, Grenoble, France
  • 2Univ. Grenoble Alpes, CNRS, LGGE UMR5183, Grenoble, France

Abstract. The dynamics of low latitude turbulent western boundary currents, subject to two different types of idealized wind forcing, Monsoon Wind and Trade Wind, is considered using numerical results from integrations of a reduced gravity shallow-water model. For viscosity values of 1000 m2 s−1 and above, the boundary layer dynamics compares well to the analytical solutions of the Munk-layer and the inertial-layer, derived from quasigeostrophic theory. Modifications due to variations in the layer thickness (vortex stretching) are only important close to the boundary. When the viscosity is reduced the boundary layer becomes turbulent and coherent structures in form of anticyclonic eddies, bursts (violent detachments of the viscous sub-layer) and dipoles appear. Three distinct boundary layers emerge, the viscous sub-layer, the advective boundary layer and the extended boundary layer. The first is characterized by a dominant vorticity balance between the viscous transport and the advective transport of vorticity. The second by a balance between the advection of planetary vorticity and the advective transport of relative vorticity. The extended boundary layer is the area to which turbulent motion from the boundary extends. The scaling of the three boundary layer thicknesses with viscosity is evaluated.

A pragmatic approach to determine the eddy viscosity diagnostically for coarse resolution numerical models is proposed.

C. Q. C. Akuetevi and A. Wirth

 
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

C. Q. C. Akuetevi and A. Wirth

C. Q. C. Akuetevi and A. Wirth

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