squeeze length-1 dimension awi-esm-1-1-lr sea ice variables

[brittaGrusdt]

Description

Removes length-1 dimension 'nodes' for model awi_esm_1_1_lr for sea ice variables (sea ice extent north + south and sea ice area north + south) which is expected to have only a time dimension.

Closes #issue_number

Link to documentation:

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[valeriupredoi]

LGTM and with many thanks! I also checked iris.utils.squeeze is a lazy op - @schlunma mind a merge here pls? 🍻

[schlunma]

Thanks for you contribution @brittaGrusdt! Could you please add a tiny test for it? For some reason, the test coverage is not tested in this pull request, otherwise this would complain about missing tests.

If I understand correctly, iris.util.squeeze removes all dimensions with length 1, which might potentially remove other (wanted) dimensions. It might be safer to actually remove the nodes dimension manually, e.g. with

if cube.coords("nodes"):
    idx = [slice(None)] * cube.ndim
    idx[cube.coord_dims("nodes")[0]] = 0  # assumes the "nodes" coordinate is 1D
    cube = cube[tuple(idx)]  # removes "nodes" coordinate by demoting it to a scalar coordinate

[brittaGrusdt]

Thank you @valeriupredoi, @schlunma. Right, squeeze would remove all length 1 dimensions, I updated the fix so that now only the length-1 dimension 'nodes' is removed as you suggested. And I added a small test for the fix. Doing that, I saw that the two tests for allvariables are identical, i.e. the one for testing when the metadata should be fixed and the one where it doesn't need to be fixed. Shall I update this too, as part of this pr? It's just a copy paste error where the metadata for the sample data is set..

[brittaGrusdt]

I just realized that the new fix does not work (not speaking for my test, which did pass). I'll update it

[brittaGrusdt]

The problem was that the data in the original file had a dimension of length 1 without a coordinate. The error showed that it is the nodes dimension, but apparently it had been removed in some previous step, I guess. So now the fix removes a dimension of length 1 if it does not have a mapped coordinate or if its of length 1 and is nameed 'nodes'. In the test, I test both cases now.

[schlunma]

Great, thanks so much @brittaGrusdt! Just a tiny comment about type hints, apart from that I think this is ready to go!

[schlunma]

Ah, forgot one thing: If you'd like, you can add yourself to our .zenodo.json and CITATION.cff files to get acknowledgement for you contributions 👍

I will briefly close and re-open the PR to check if that fixes the cla check.