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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.

Part 1

(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).

Part 3
(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:

> Greetings,
> 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
> http://www.cgd.ucar.edu/oce/klindsay/ocmip/physics_template.html
> The code itself is located at
> http://www.cgd.ucar.edu/oce/klindsay/ocmip/write_nc_phys.f
> If you have questions about the code or find problems with it, please feel
> free to ask me.
> Thanks,
> Keith

   James Orr                      
   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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