[MITgcm-support] Re: heat fluxes and density

[Martin Losch]

Dan,

I agree with Ed, use something more recent like checkpoint56. I don't 
see any reason why you  would want to use a version that is even older 
than Release 1 (not that that is up to date (o: ).

Your questions:
1. Density: besides the matlab script that Ed suggested I have one for 
the eosType=MDJWF, which I am happy to share, and there is one for 
POLY3 in the downloaded code: utils/matlab/dens_poly3.m. For a linear 
equation of state you'll have to do it yourself, but that shouldn't be 
hard.
For "online"-output, you'd have to include code to output density, and 
that would work only if you used one tile/processor. I would refrain 
from doing that unless you want temporal averages.

2. Diagnose heat fluxes: with a later checkpoint, you'd be able to 
output diagnosed heat and (virtual) salt fluxes directly by turning on 
time-averaging (set timeaveFreq to something finite in data). If you 
don't want to do that, you'll have to diagnose it from the output and 
your restoring fields in the following way:
(Tsurf-Trestore)*dz*Cp*rhoNil/tauTheta,
where Tsurf is the surface temperature of the model, Trestore your 
restoring temperature, dz the layer thickness of your top layer, Cp the 
heat capacity (either the default 3994.0 or whatever you set it to in 
data), rhoNil a constant reference density (default 999.8 or whatever 
you set it to in data), and tauTheta the restoring timescale 
(tauThetaClimRelax in data).

Martin

On Nov 29, 2004, at 7:49 AM, Ed Hill wrote:

>
>>> From: Dan Conipo <dconipo at yahoo.com>
>>> Subject: heat fluxes and density
>>> Date: Mon, 29 Nov 2004 02:49:48 -0800 (PST)
>>> Hi,
>>> I'm a new user of the code. I'm using a version c39.
>>> I would like to know
>>> 1. if there is a way to compute the density automatically, as a
>>> output variable. Have you any suggestions to do that in MatLab? I
>>> should plot the vertical circulation as a function of density and
>>> not depth.
>>> 2. if it's possible to compute the heat fluxes starting from a
>>> restoring sst to force the circulation.
>>>
>>> Please, reply me.
>
>
> Hi Dan,
>
> We *strongly* recommend that you use a more recent version.  A large
> number of bugs have been fixed and features added since "checkpoint39"
> was released way back in May, 2001.  A far better choice would be
> checkpoint56 which can be obtained at:
>
>   http://mitgcm.org/download/MITgcm_checkpoint56.tar.gz
>
> And in regards to your questions:
>
>  1) Depending upon which EoS you use, density can be computed
>     off-line (that is, after the model has been run) from
>     depth, salinity, and temperature using the following
>     MatLAB scripts:
>
> http://mitgcm.org/cgi-
> bin/viewcvs.cgi/MITgcm_contrib/high_res_cube/eddy_flux/densjmd95.m
> http://mitgcm.org/cgi-
> bin/viewcvs.cgi/MITgcm_contrib/high_res_cube/eddy_flux/eh3densjmd95.m
>
>     Otherwise, its fairly easy to modify MITgcm to output
>     the densities directly.
>
>  2) Someone else will have to help you with the heat flux
>     calculations -- I'm not as familiar with them.
>
> Ed
>
> -- 
> Edward H. Hill III, PhD
> office:  MIT Dept. of EAPS;  Rm 54-1424;  77 Massachusetts Ave.
>              Cambridge, MA 02139-4307
> emails:  eh3 at mit.edu                ed at eh3.com
> URLs:    http://web.mit.edu/eh3/    http://eh3.com/
> phone:   617-253-0098
> fax:     617-253-4464
>
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