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SUMMARY:Modelling the interactions of near-inertial waves and vortical mot
 ion in the ocean - Vanneste\, J (University of Edinburgh)
DTSTART:20131203T144500Z
DTEND:20131203T153000Z
UID:TALK49146@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Co-author: Eric Danioux (University of Edinburgh) \n\nWind for
 cing of the ocean generates a spectrum of inertia-gravity waves that is sh
 arply peaked near the local inertial (or Coriolis) frequency. The correspo
 nding near-inertial waves (NIWs) make a dominant contribution to the verti
 cal velocity and vertical shear in the ocean\; they therefore play an impo
 rtant role for mixing\, biological productivity\, pollutant dispersion and
 \, arguably\, the thermohaline circulation. An asymptotic model proposed b
 y Young and Ben Jelloul describes the slow evolution of NIWs that results 
 from weak dispersion and from their interactions with the quasi-two-dimens
 ional vortical motion. We derive this YBJ model by applying a form of Whit
 ham averaging to the variational formulation of the primitive equations fo
 r a rotating stratified fluid. This provides a direct route to the YBJ equ
 ation and elucidates its variational structure and conservation laws. We t
 hen consider the effect of turbulent vortical motion (modelled as a homoge
 neous random field) of a scale similar to that of the waves. Specifically\
 , we derive a transport equation for NIWs that describes their scattering 
 by the vortical motion and show how this scattering leads to an isotropiza
 tion of the NIW field. Direct numerical simulations of the YBJ equations a
 re used to test the predictions of the transport equation. Possible models
  of the two-way coupling between NIWs and vortical motion are also discuss
 ed.\n
LOCATION:Seminar Room 1\, Newton Institute
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