[MITgcm-support] Modelling at the Poles

[Jean-Michel Campin]

Hi Benjamin,

trying to clarify few things regarding pkg/exch2 and grids:
1) If you use a non-obvious subdomain topology, e.g., cubed-sphere type topology
   (in this case: useCubedSphereExchange=.TRUE., in eedata), you need to use pkg/exch2.
  If it's a regular cube (squared faces) without blank tile, default setting works
  fine and you don't need parameter file "data.exch2"; Otherwise, e.g. Lat-Lon cap
  grid or with blank tiles, you will need to set few parameters in "data.exch2"
  There are examples of data.exch2 for lat-lon cap grids in MITgcm_contrib, e.g. here:
   MITgcm_contrib/gael/verification/global_oce_llc90/input.ecco_v4/data.exch2
  or here:
   MITgcm_contrib/llc_hires/llc_270/input/data.exch2
  and some example also (with a README file there) here:
   MITgcm/utils/exch2/input/data.exch2.*
2) If you are using a simple grid topology (e.g., cartesian grid, SphericalPolarGrid,
  or curvilinear grid all in 1 piece, i.e, single face), you can use pkg/exch2
  (and without useCubedSphereExchange=T and without blank tile, the default pkg/exch2 
  setting works) but you don't need to except if you have blank tiles.
  The verification experiment: verification/global_ocean.90x40x15 is an example of 
  a simple grid set-up using pkg/exch2:
   a) without blank tile if non-MPI built & run (code/SIZE.h, dont'use any data.exch2)
   b) with blank tiles if building and running with MPI (code/SIZE.h_mpi, input/data.exch2.mpi)
3) If you want to use a curvilinear grid (usingCurvilinearGrid=.TRUE.,), you need to specify
  file(s) containing all the grid information (horizGridFile= ...). 
  It could be usefull to start by using an already existing grid as Dimitris suggested.
  And from there, you could try to generate your own grid file(s). One thing to keep
  in mind is that, for now, MITgcm only supports locally orthogonal grids.
  Again, you can decide not to use pkg/exch2 if the grid is all in one piece (and no blank
  tile is used).
  
Cheers,
Jean-Michel

On Sat, Apr 16, 2016 at 09:17:13AM -0600, Benjamin Ocampo wrote:
> Hi Dimitris:
> 
> Thank you for the response. I will run cs_4km code and determine how I can
> set the latitude and
> longitude ranges including the resolution.
> 
> Cheers,
> Benjamin
> 
> On Sat, Apr 16, 2016 at 5:53 AM, Menemenlis, Dimitris (329C) <
> Dimitris.Menemenlis at jpl.nasa.gov> wrote:
> 
> > There is a couple example MITgcm Arctic Ocean configurations here:
> > http://mitgcm.org/viewvc/MITgcm/MITgcm_contrib/arctic/
> > and here: http://mitgcm.org/viewvc/MITgcm/MITgcm_contrib/arctic40km/
> >
> > On Apr 15, 2016, at 9:59 PM, Benjamin Ocampo <rurik at ualberta.ca> wrote:
> >
> > Hi All:
> >
> > My apologies if I have been littering the support with unanswerable
> > questions but
> > I appear to be at a conundrum.
> >
> > My current objective is to try to get a spherical regional model to
> > successfully work
> > at the North pole but I am at a loss. As far as I know, there exists a
> > singularity
> > at latitude = 90N due to the spherical laplacian term in the Navier-Stokes
> > equation and hence convenctional lat-lon grids do not work.
> >
> > Thus, I have read into using the exch2 package to determine if it is
> > feasible to
> > get a regional model working at the North Pole. However, I am at a loss as
> > I am
> > not familiar in setting up the data.exch2 file (for a single face) with a
> > fixed lat-lon
> > domains (eg. 0E to 360E, 80N to 90N or 0E to 360E, -90N to -80N) with
> > dlat and dlon resolution (eg. dlat = 0.1,dlon = 0.1 resolution).
> >
> > Does using the package exch2 provide a feasible method for regional
> > modelling at the poles? If so, how do I correctly set up the data.exch2
> > file?
> >
> > Cheers,
> > Benjamin
> > _______________________________________________
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> > MITgcm-support at mitgcm.org
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> >
> >
> >
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> >

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