[MITgcm-support] MNC grid boundaries with curvilinear coordinates

[Martin Losch]

David,

it's great to see python output in this matlab-dominated community (o:

It's not a bug, it's a feature: the default boundary conditions for the MITgcm are double periodic so that the point at i=nx+1 is identical to the point at i=1, and the same for the j-direction. In the mnc-package, the output for variable on u and v-points of each tile is augmented by the first column/row of the neighboring tile, as a service (o: The last tile in x get's the first column of the first tile in x, and the coordinate it necessarily XG(1) = XG(end) - Lx.

If your domain it periodic, that's what you want, right? If not, you can just ignore the last column. In fact, the standard mds output (the *.data/meta files) do not have these extra columns for any of the variables, neither for XG/YG.

Martin

On Feb 22, 2013, at 5:21 PM, David Huard <david.huard at gmail.com> wrote:

> Hi all, 
> 
> I'm using the MITgcm on the Arctic domain and I noticed an issue with the netcdf output grid variables XG and YG. 
> 
> The last row and column of XG and YG are just copies the first row and column, as if it was a pac-man domain. Here is an example: 
> 
> array([[  31.97116089,   32.10241318,   32.23471451, ...,  146.66885376,
>          146.80964661,   31.97116089],
>        [  31.77091026,   31.90175247,   32.033638  , ...,  146.87324524,
>          147.01361084,   31.77091026],
>        [  31.57006645,   31.70048714,   31.83195305, ...,  147.07829285,
>          147.21824646,   31.57006645],
>        ..., 
>        [ -48.62563324,  -48.77060318,  -48.91656113, ..., -129.88247681,
>         -130.03565979,  -48.62563324],
>        [ -48.7310524 ,  -48.87626648,  -49.02246475, ..., -129.77496338,
>         -129.92831421,  -48.7310524 ],
>        [  31.97116089,   32.10241318,   32.23471451, ...,  146.66885376,
>          146.80964661,   31.97116089]])
> 
> 
> The consequence is that the last row and column of the tracer coordinates (XC, YC) do not lie in between the surrounding grid coordinates, which is what I would be expecting. 
> 
> Note that I generated the full grid using the python gluemncbig script. 
> 
> Cheers, 
> 
> David Huard
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