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Optionally support C-grid connectivity in deseas #37

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aekiss opened this issue Oct 16, 2024 · 7 comments · May be fixed by #39
Open

Optionally support C-grid connectivity in deseas #37

aekiss opened this issue Oct 16, 2024 · 7 comments · May be fixed by #39
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@aekiss

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@aekiss
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aekiss commented Oct 16, 2024

Hi @micaeljtoliveira, does deseas assume B-grid connectivity requirements? I guess this is controlled by the choke criteria in topography_number_seas? https://github.com/COSIMA/domain-tools/blob/master/src/topography.f90#L225

i.e. will we need to change this to allow marginal seas to be regarded as connected to the ocean when the outlet is 1 cell wide on a C-grid (e.g. Gibraltar)?
@micaeljtoliveira
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@aekiss Yes, my understanding is that it does assume B-grid connectivity.

I don't remember anymore all the details of the algorithm, but I think this is the relevant piece of code:

domain-tools/src/topography.f90

Lines 323 to 331 in ab469df

!get chokes
choke_east = .not. (any(sea(i:ip, jp) == land) .and. any(sea(i:ip, jm) == land))
choke_west = .not. (any(sea(im:i, jp) == land) .and. any(sea(im:i, jm) == land))
choke_south = .not. (any(sea(im, jm:j) == land) .and. any(sea(ip, jm:j) == land))
choke_north = .not. (any(sea(im, j:jp) == land) .and. any(sea(ip, j:jp) == land))
new_sea = min(minval([sea(im, j), sea(ip, j), sea(i, jm), sea(i, jp)], &
mask=[choke_west, choke_east, choke_south, choke_north]), land)
if (sea(i, j) /= new_sea) then
sea(i, j) = new_sea

@aekiss aekiss mentioned this issue Oct 16, 2024
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@aekiss
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aekiss commented Oct 16, 2024

ok, ta, as suspected then.

@aekiss
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aekiss commented Oct 18, 2024 •
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@micaeljtoliveira it looks to me like we could optionally support C-grid connectivity rules by simply omitting the mask argument to minval here (and also in the duplicate code for the backward sweep, lines 365-6) - does that sound right?

domain-tools/src/topography.f90

Lines 328 to 329 in ab469df

new_sea = min(minval([sea(im, j), sea(ip, j), sea(i, jm), sea(i, jp)], &
mask=[choke_west, choke_east, choke_south, choke_north]), land)

@micaeljtoliveira
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@aekiss Yes, that sounds right.

@aekiss aekiss changed the title Does deseas assume B-grid connectivity requirements? Optionally support C-grid connectivity in deseas Oct 18, 2024
@aekiss aekiss self-assigned this Oct 21, 2024
aekiss added a commit that referenced this issue Oct 21, 2024
@aekiss
optionally support c-grid connectivity in deseas - #37
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@aekiss aekiss linked a pull request Oct 21, 2024 that will close this issue
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@aekiss
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aekiss commented Oct 22, 2024

Just for reference, mom6-regional has this code for removing narrow channels https://github.com/COSIMA/regional-mom6/blob/0bfe4ba7aab3f27821476b83130861d6922a6c80/regional_mom6/regional_mom6.py#L1311

@aekiss
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aekiss commented Oct 22, 2024 •
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@micaeljtoliveira, @angus-g do you know whether topography_nonadvective is necessary for MOM6? We don't want to do coastal, but is potholes worthwhile on a z* vertical grid (using different criteria to suit a C grid)? I guess I'm asking, does anything bad happen if a cell is surrounded on all sides by vanishing layers? (I'm guessing it's fine)

domain-tools/src/topography.f90

Line 495 in ab469df

subroutine topography_nonadvective(this, vgrid_file, vgrid_type, potholes, coastal, fix)

@angus-g
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angus-g commented Oct 23, 2024

I guess I'm asking, does anything bad happen if a cell is surrounded on all sides by vanishing layers? (I'm guessing it's fine)

As long as it's wet on all those sides, I don't think there's an issue, no.

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support C-grid connectivity in deseas COSIMA/domain-tools
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@angus-g @micaeljtoliveira @aekiss