Séminaire : Milan Kloewer (Atmospheric, Oceanic and Planetary Physics, University of Oxford): Energy budget-based backscatter in a shallow water model of a double gyre basin
Monday 01 April 2019, 11:00am - 12:00pm
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Abstract : The parameterization of sub-grid scale processes is one of the key
challenges towards improved numerical simulations of the atmospheric and
oceanic circulation. Numerical weather prediction models as well as
climate models would benefit from more sophisticated turbulence closures
that allow for less spurious dissipation at the grid-scale and
consequently higher and more realistic levels of eddy kinetic energy
(EKE). Recent studies propose to use a hyperviscous closure in
combination with an additional deterministic forcing term as a negative
viscosity to represent backscatter of energy from unresolved scales. The
sub-grid EKE is introduced as an additional prognostic variable that is
fed by dissipation at the grid scale, and enables recycling of EKE via
the backscatter term at larger scales. This parameterization was
previously shown to work well in zonally re-entrant channel
configurations. Here, a generalization in the form of a Rossby
number-dependent scaling for the strength of the backscatter is
introduced to represent the emergence of a forward energy-cascade in
unbalanced flows near the boundaries. We apply the parameterization to a
shallow water model of a double gyre basin and provide evidence for its
general applicability. In terms of mean state and variability, a low
resolution model is considerably improved towards a high resolution
control run at low additional computational cost. Although this study
focuses on an idealized shallow water model, a very recent study has
successfully implemented the parameterization into a 3D primitive
equation model, which is capable of simulating on unstructured and
variable-resolution grids. This perspective for global ocean models is
briefly presented as an outlook.
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Location salle de réunion LOCEAN, tour 45/55, 4eme étage



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