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Re: model physics NetCDF template
I'm glad you've put together the template for requesting the model output
for the OCMIP physics comparison. I have four comments concerning your Web
info on this.
(1) NET surface Heat and Freshwater fluxes:
Some clarification requested. For example, models that use both
climatological values + T,S restoring, I assume you mean the sum
of both should be saved. both. If so, you should state this to
leave no room for misunderstanding. Also for models that use such
a "double" restoring term, it could be useful to have both fields.
We could then compare differences in the restoring term as well.
(2) Mixed layer depth:
How this is defined? Different modeling groups use different
criteria, so there seems a need to be more specific here. I've
seen modelers use three different definitions: (1) some use a
density criterion, (2) some use just the top model layer, and (3)
in IPSL, we prefer to use a criterion based on the magnitude of
Kz, predicted by the TKE model.
(3) Rotation of velocities (Point 2):
Your philosophy here won't work very well, for non-B grids,
particulary the curvilinear variety. As you know B grids have u
and v points at coincident locations, but such is not the case
with C grids (u and v on perpendicular faces of each tracer-grid
box). Interpolating u and v on a curvilinear C grid to one point
(as necessary to provide your requested zonal and meridional
velocities) is difficult to do without substantial error. For
example, experience at IPSL shows that such interpolation can
produce some very wrong meridional heat fluxes.
I do not know one best way to get around this difficulty, but
there seem a couple of alternatives. One solution would be to ask
for u and v on the original grid and in the sense of the grid (for
curvilinear models). We could then use existing programs, such as
we have here at IPSL, to precisely calculate meridional transport
for the "special" models. A simpler solution might be to ask each
group to send their calculated meridional transport (lat
vs. depth) for each basin. In any case, I think this point
deserves more discussion. We need some advice from those with
weird grids (UL, MPI, AWI, IPSL).
(1) item 6 (u,v mask):
May also need some input here from those that use partially filled
grid boxes near the bottom (MPI, MIT) and sides (AWI) of the ocean.
On Thu, 17 Feb 2000, Keith Lindsay wrote:
> To facilitate comparisons of ocean model physics, I have written a
> template to generate a NetCDF file containing basic physics fields. We
> request that each modeling group use this template and provide the
> resulting NetCDF file to us for model physics comparison.
> An HTML document describing the template and its use is located at
> The code itself is located at
> If you have questions about the code or find problems with it, please feel
> free to ask me.
Laboratoire des Sciences du Climat et de l'Environnement
Unite Mixte de Recherche CEA-CNRS
LSCE, CEA Saclay http://www.ipsl.jussieu.fr/~jomce
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