[MITgcm-support] Resources for generating curvilinear grid for MITgcm (displaced-pole Arctic)

[Dimitris Menemenlis]

Hi Sam, in case helpful, there is a couple of readily-available Arctic Ocean grids with displace poles, for example,

ASTE:
https://doi.org/10.1029/2020MS002398
https://github.com/crios-ut/aste

the SASSIE ECCO model:
https://doi.org/10.1029/2025GL118871

and a series of cube-sphere-derived Arctic faces, e.g.,
https://github.com/MITgcm-contrib/arctic
https://doi.org/10.1016/j.ocemod.2010.02.002
https://doi.org/10.1016/j.ocemod.2009.12.008
https://doi.org/10.1029/2010JC006573
https://doi.org/10.5194/tc-11-1553-2017

Cheers, Dimitris


> On Feb 23, 2026, at 12:23 PM, Jean-Michel Campin <jmc at mit.edu> wrote:
> 
> Hi Sam,
> 
> There is a way to "rotate" the lat-lon grid to move the N & S pole elsewhere.
> this is done by setting the 3 rotation angle: phiEuler, thetaEuler, psiEuler
> 
> From PARAMS.h:
> C     rotateGrid      :: rotate grid coordinates to geographical coordinates
> C                        according to Euler angles phiEuler, thetaEuler, psiEuler
> 
> And the piece of code that does the rotation is: rotate_spherical_polar_grid.F
> called from: ini_spherical_polar_grid.F
> 
> Cheers,
> Jean-Michel
> 
> On Sun, Feb 22, 2026 at 02:58:49PM -0500, Sam Phillips wrote:
>> Hi all,
>> 
>> I'm setting up a barotropic, wind-forced Arctic Ocean simulation on a
>> displaced-pole curvilinear grid (pole at -40E, 75N over Greenland), NX=1530
>> NY=520 at ~10.7km resolution, single vertical level just as a baseline.
>> 
>> I'm running into what appear to be grid generation problems - my mitgrid
>> metrics show implausible values (dxF and dxC with minimums around 22m on a
>> nominally 10.7km grid, dyC constant everywhere, rAz reaching zero) that I
>> believe are causing immediate cg2d divergence.
>> 
>> Before going further with debugging, I'd like to go back to basics and
>> generate a proper mitgrid file. I'm currently using a Python-based workflow
>> but I'm open to anything. A few specific questions:
>> 1. Is there a recommended tool or workflow for generating displaced-pole
>> curvilinear grids for MITgcm?
>> 2. Are there example mitgrid files or grid generation scripts for Arctic or
>> regional curvilinear configurations that I could use as a reference?
>> Googling hasn't proven very helpful.
>> 3. Is there anything specific to watch out for when the displaced pole
>> falls over land (Greenland in my case) in terms of how the grid metrics
>> behave near the seam?
>> 
>> Any pointers to scripts, papers, or configurations that have worked for
>> similar domains would be very helpful.
>> 
>> Thanks,
>> Sam
> 
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