Solve naming conflict for using cross_section on ICON data

[tdoerff]

Closes #1425

Overview

• in UxDataArrayCrossSectionAccessor: retrieve the name of the longitude / latitude coords from the input UxDataArray and update the coords of the output Dataset accordingly.

Expected Usage

Input data can be obtained here: https://kumulus.iap-kborn.de/index.php/s/qHiQFKzoA5Jwn2X

import uxarray as ux

data_path = "uvwtemp_3d_ML_19790124T000000Z.nc"
grid_path = "icon_grid_0013_R02B04_G.nc"

uxds = ux.open_dataset(grid_path, data_path)

cross_section_gca = uxds.temp.cross_section(start=(0, -90), end=(0., 90))

PR Checklist

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Testing

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Examples

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[rajeeja]

Cross-section on ICON data fails now because the input has face coords clon/clat and we drop n_face, so the accessor tries to add new lat/lon coords on steps and triggers CoordinateValidationError (“clon has dimensions ('n_face',) but these are not a subset of ('time','height','steps')”) @tdoerff thanks for reporting this and providing this fix. I think the new lat_key/lon_key logic introduces problems: it always writes four coordinates (lat, lon, plus lat_key/lon_key) - can we do something better? How about we pick the existing face lat/lon coord names once (fallback to lat/lon if none) and attach only those so we don’t duplicate or clobber other coords.

[erogluorhan]

Thanks for your contribution! It looks like this issue is related to our ICON I/O rather than cross-sections though. I think we missed dim/coord name parsing when opening ICON data/grid in uxarray, which can be fixed easily. @rajeeja does this make sense?

[tdoerff]

Hi, thanks for the feedback!

@rajeeja you wrote:

How about we pick the existing face lat/lon coord names once (fallback to lat/lon if none) and attach only those so we don’t duplicate or clobber other coords.

I think the new logics should in fact do the trick. lat_key_cands and lon_key_cand contain all labels containing the substrings "lat"/"lon", ie, either "clat"/"clon" or "lat"/"lon". If there are no candidates then we use "lat"/"lon" as fallback. Maybe a systematic test would be nice.

@erogluorhan This is a good point. Do you think it would be a better solution to rename the "clon"/"clat" dimension names in _icon._primal_to_ugrid()?

[erogluorhan]

@erogluorhan This is a good point. Do you think it would be a better solution to rename the "clon"/"clat" dimension names in _icon._primal_to_ugrid()?

Yeah, probably something like that. I recall we have good dim/coord naming parsers in _mpas._primal_to_ugrid() and _mpas._dual_to_ugrid(), so we will need to reuse ideas from them into parsers in ICON.

[rajeeja]

Hi, thanks for the feedback!

@rajeeja you wrote:

How about we pick the existing face lat/lon coord names once (fallback to lat/lon if none) and attach only those so we don’t duplicate or clobber other coords.

I think the new logics should in fact do the trick. lat_key_cands and lon_key_cand contain all labels containing the substrings "lat"/"lon", ie, either "clat"/"clon" or "lat"/"lon". If there are no candidates then we use "lat"/"lon" as fallback. Maybe a systematic test would be nice.

@erogluorhan This is a good point. Do you think it would be a better solution to rename the "clon"/"clat" dimension names in _icon._primal_to_ugrid()?

@tdoerff please check #1430