[MITgcm-support] Re: MITgcm-support Digest, Vol 20, Issue 15

eliyahu biton eliyahu.biton at weizmann.ac.il
Tue Feb 22 03:10:15 EST 2005

mitgcm-support-request at mitgcm.org wrote:

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>Today's Topics:
>   1. Re: [Fwd: Auto-discard notification] (Jean-Michel Campin)
>   2. exf forcing (Mike Spall)
>   3. Re: exf forcing (Patrick Heimbach)
>   4. Re: exf forcing (Dimitris Menemenlis)
>   5. Fwd: boundary conditions and biharmonic damping (Ed Hill)
>Message: 1
>Date: Thu, 17 Feb 2005 12:33:43 -0500
>From: Jean-Michel Campin <jmc at ocean.mit.edu>
>Subject: Re: [MITgcm-support] [Fwd: Auto-discard notification]
>To: mitgcm-support at mitgcm.org
>Message-ID: <200502171733.j1HHXhZP027867 at ocean.mit.edu>
>Hi Eli,
>>>Hello! I have downloaded the MITgcm code and using it to
>>>investigate the red sea. To this end I'm running the model
>>>(version 56) with exf, cal, obcs packages (just one open
>>>boundary on the east side). The red sea is a narrow(~300 km)
>>>and elongated basin (~2000 km). As the main axis points to
>>>the NW, about three quarter of the grid points are 'land'
>>>points (indicated by zero at the bathymetry input file). At
>>>one of the test experiment I conducted, I have found that
>>>computation time for land points is almost the same as the
>>>'sea' grid point (is it correct?). Following this, I would
>>>like to rotate the main axis by ~45 degree which will allow
>>>me to reduce the number of grid points dramatically and my
>>>computation time too. So my question is if there is any
>>>smart way to do this, but still preserve real Coriolis
>>>parameters (is there a way to insert as an input file ?)
>>>and volume conservation. Alternatively is there a way to
>>>reduce somehow computation time of 'land grid point'
>>>(which will make the work much easier). thanks Eli
>The simplest way to go would be to rotate by 45^o and
>to change the coriolis initialisation: model/src/ini_cori.F
>I also added recently a way to read coriolis (fCori, fCoriG
>& fCoriCos) from files (see at the end of ini_cori.F) but
>you still need to change the default to activate this part
>of the code.
>Are you using cartesianiGrid or sphericalPolarGrid ? 
>Message: 2
>Date: Thu, 17 Feb 2005 14:50:51 -0500
>From: Mike Spall <mspall at whoi.edu>
>Subject: [MITgcm-support] exf forcing
>To: mitgcm-support at mitgcm.org
>Message-ID: <4214F59B.2050105 at whoi.edu>
>Content-Type: text/plain; charset=us-ascii; format=flowed
>Hi All,
>Another question regarding the exf package.  I can see that
>there is an option to provide the forcing fields on a grid
>other than that used by the ocean model, but it is not
>clear to me how to set that up.  Is there an example of
>how to specify the input (forcing) grid spacing, location,
>and interpolation method?
Hi Jean-Michel and others !

Thanks for the quick reply.

First, to answer your question, I'm using sphericalPolarGrid in order to 
preserve volume, and using real Coriolis values. But for the rotated 
basin I will be forced to use cartesianGrid with real Coriolis 
parameters as an input file, and change the grid resolution along the x 
and y axis to in order to preserve the volume. I tried to insert real 
Coriolis parameters (fCori, fCoriG, fCoriCos) as input files within the 
file 'data' at PARAM03/05 and the model didn't run (I think that the 
problem is that the parameters fCori, fCoriG and fCoriCos don't show up 
in the MITgcm/model/scr/ini_params.F subroutine). I would like to know 
what I need to do in order to insert the Coriolis parameters as an input 
file .

Another question if I may: I just want to be sure, is the computation 
time for 'land grid point' (those indicated by zero values within the 
bathimetry file) the same as the 'sea grid point' ?

Thanks Eli

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