1 research outputs found
Scale-awareness in an eddy energy constrained mesoscale eddy parameterization
There is an increasing interest in mesoscale eddy parameterizations that are
scale-aware, normally interpreted to mean that a parameterization does not
require re-tuning of parameters as the model resolution changes. Here we
examine whether Gent--McWilliams (GM) based version of GEOMETRIC, a mesoscale
eddy parameterization that is constrained by a parameterized eddy energy
budget, is scale-aware in its energetics. It is generally known that GM-based
schemes severely damp out explicit eddies, so the parameterized component would
be expected to dominate across resolutions, and we might expect a negative
answer to the question of energetic scale-awareness. A consideration of why
GM-based schemes damp out explicit eddies leads a suggestion for what we term a
splitting procedure: a definition of a `large-scale' field is sought, and the
eddy-induced velocity from the GM-scheme is computed from and acts only on the
large-scale field, allowing explicit and parameterized components to co-exist.
Within the context of an idealized re-entrant channel model of the Southern
Ocean, evidence is provided that the GM-based version of GEOMETRIC is
scale-aware in the energetics as long as we employ a splitting procedure. The
splitting procedure also leads to an improved representation of mean states
without detrimental effects on the variability.Comment: 26 pages, 8 figures, 1 table. Previous version has data generated
from a bugged NEMO implementation of GEOMETRIC, and the results from the
previous version could be regarded as a case where GEOMETRIC is used
***without*** mean flow advection of parameterised eddy energy. This bug is
fixed in the present version, with minor updates to the article to reflect
the chang