Add CORDEX domain target grids for regridding by ghossh · Pull Request #3096 · ESMValGroup/ESMValCore

ghossh · 2026-06-01T14:58:47Z

Description

Adds support for using standard CORDEX domain names, such as EUR-11, as target_grid values in the regrid preprocessor.

Previously, target_grid: EUR-11 was treated as an MxN grid specification and failed with:

ValueError: Invalid MxN cell specification for grid, got 'EUR-11'.

Closes #3088

Link to documentation:

https://esmvaltool--3096.org.readthedocs.build/projects/ESMValCore/en/3096/recipe/preprocessor.html#regridding-on-a-cordex-domain-grid

Checklist

It is the responsibility of the author to make sure the pull request is ready to review. The icons indicate whether the item will be subject to the 🛠 Technical or 🧪 Scientific review.

🧪 The new functionality is relevant and scientifically sound
🛠 This pull request has a descriptive title and labels
🛠 Code is written according to the code quality guidelines
🧪 and 🛠 Documentation is available
🛠 Unit tests have been added
🛠 Changes are backward compatible
🛠 The list of authors is up to date
🛠 All checks below this pull request were successful

CLAassistant · 2026-06-01T14:58:59Z

All committers have signed the CLA.

codecov · 2026-06-01T15:00:20Z

Codecov Report

❌ Patch coverage is 46.15385% with 21 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.01%. Comparing base (4127673) to head (a96e132).
⚠️ Report is 40 commits behind head on main.

Files with missing lines	Patch %	Lines
esmvalcore/preprocessor/_regrid.py	44.73%	21 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3096      +/-   ##
==========================================
- Coverage   96.14%   96.01%   -0.13%     
==========================================
  Files         267      267              
  Lines       15771    15803      +32     
==========================================
+ Hits        15163    15174      +11     
- Misses        608      629      +21

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bouweandela

Looks like a great start! Could you take a look at the checklist? A few things to do would be

sign the CLA
add a unit test
add documentation

Usually you can find advice on how to go about that in the pull request template, but in case you missed it you can find it here: https://github.com/ESMValGroup/ESMValCore/blob/main/.github/pull_request_template.md

bouweandela · 2026-06-02T07:52:23Z

+        Dummy cube with rotated-pole dimension coordinates and geographical
+        auxiliary coordinates matching the official domain specification.
+    """
+    domain = cx.cordex_domain(domain_name, bounds=True)


Maybe you could simplify this code by using ncdata.iris_xarray.cubes_to_xarray to convert the xarray.Dataset to an iris.cube.Cube directly?

This is a bit simpler, but not much. What I meant was something like

domain = cordex.domain(domain_name, bounds=True).reset_coords() # Add a mock variable. domain["data"] = xr.zeros_like(domain.lon) # Associate the grid mapping and coordinates with the data. domain.data.attrs = { "coordinates": "lat lon", "grid_mapping": "rotated_latitude_longitude", } # Associate the bounds with the coordinates. domain.lat.attrs["bounds"] = "lat_vertices" domain.lon.attrs["bounds"] = "lon_vertices" cube, = ncdata.iris_xarray.cubes_from_xarray(domain) cube.coord("grid_latitude").guess_bounds() cube.coord("grid_longitude").guess_bounds()

…ion and streamline coordinate handling

…nstruction tests

This update introduces a new section in the preprocessor documentation detailing how to regrid to standard CORDEX domains using the `target_grid` parameter. An example configuration for the `EUR-11` domain is provided, clarifying the use of domain names recognized by the `cordex` package.

ghossh · 2026-06-08T14:01:57Z

Hi @bouweandela , Please provide another review. Not sure why the workflow commit is failing!

ghossh · 2026-06-09T14:10:06Z

Hi @bouweandela , I found that in case of :

  - project: CORDEX
    domain: EUR-11
    dataset: RACMO22E
    driver: CNRM-CERFACS-CNRM-CM5
    ensemble: r1i1p1
    institute: KNMI
    rcm_version: v2

in this line, it's failing due to no having bounds

ESMValCore/esmvalcore/preprocessor/_regrid.py

Line 1017 in ddd67d7

if not np.allclose(coord1.bounds, coord2.bounds):

A possible solution could be like adding this:

        if not coord1.has_bounds() or not coord2.has_bounds():
            return False

what do you think?

bouweandela · 2026-06-09T14:39:38Z

Not sure why the workflow commit is failing!

Should be fixed by #3104

bouweandela · 2026-06-10T11:20:58Z

Regarding the no-bounds issue: this seems unrelated to the changes in this pull request, so it would be great if you could open a new issue for this. We can then make a plan for how to solve it there and tackle it in a new pull request.

bouweandela · 2026-06-10T12:27:15Z

+    -------
+    bool
+        Whether ``spec`` is recognised by :mod:`cordex`.
+    """


Suggested change

"""

"""

if not isinstance(spec, str):

return False

Adding this here would avoid the extra nesting in the places where you're calling this function, making that code a bit easier to read.

bouweandela · 2026-06-10T12:30:38Z

        Alternatively, a :class:`~esmvalcore.dataset.Dataset` can be provided.
        Alternatively, a string cell specification may be provided,
        of the form ``MxN``, which specifies the extent of the cell, longitude
        by latitude (degrees) for a global, regular target grid.


Please also mention that this can be a CORDEX domain here

bouweandela · 2026-06-10T12:33:47Z

+          target_grid: EUR-11
+          scheme: linear
+
+Any domain name recognized by the ``cordex`` package can be used, for example


It would be nice to add a link to this page so users can find the available domains easily.

bouweandela · 2026-06-10T12:34:13Z

+domain definition instead of interpreting the value as an ``MxN`` grid
+specification.


Suggested change

domain definition instead of interpreting the value as an ``MxN`` grid

specification.

domain definition.

would suggest leaving that out as it doesn't add much

bouweandela · 2026-06-10T12:39:52Z

+    assert target.coord(var_name="rlon") is not None
+
+
+def test_update_target_grid_accepts_cordex_domain():


Nice that you're adding tests for this! I think this would be a better place for them:

ESMValCore/tests/unit/recipe/test_recipe.py

Line 809 in ddd67d7

def test_update_regrid_time():

bouweandela · 2026-06-10T12:41:45Z

+def test_get_target_grid_cube_cordex_domain(global_cube):
+    """Test target grid cube construction for a CORDEX domain."""
+    target = _get_target_grid_cube(global_cube, "EUR-11")
+    assert target.coord(var_name="rlat") is not None


Suggested change

assert target.coord(var_name="rlat") is not None

assert target.coords(var_name="rlat")

would test that there is at least one coordinate with the name "rlat". The iris.cube.Cube.coord method raises an exception if no coordinate is found, so it will never return None.

bouweandela

Nice progress @ghossh! I've pasted the checklist back in the pull request description to make it easier for myself to remember what to look for. A few more things to do would be to add a label to the pull request (e.g. preprocessor) and add yourself to the list of authors. Could you please also update the branch so coverage is uploaded again and I can see which lines of code have coverage.

Add CORDEX domain target grids for regridding

a96e132

ghossh requested a review from bouweandela June 1, 2026 14:58

bouweandela reviewed Jun 2, 2026

View reviewed changes

Add unit tests for CORDEX domain target grids in regridding

8e401c2

bouweandela mentioned this pull request Jun 5, 2026

CORDEX WAS-22 (and EAS-22) grid too small #3099

Closed

ghossh added 2 commits June 8, 2026 13:04

Refactor _cordex_stock_cube function to utilize xarray for grid creat…

ef94822

…ion and streamline coordinate handling

Merge branch 'main' into target-grid-cordex-domain

502047a

ghossh self-assigned this Jun 8, 2026

ghossh added 2 commits June 8, 2026 15:31

Update docstring in global_cube fixture for clarity in target-grid co…

0bd0814

…nstruction tests

ghossh requested a review from bouweandela June 8, 2026 13:56

ghossh added this to Cordex support (ESO4clima WP2) Jun 9, 2026

ghossh moved this to In Progress in Cordex support (ESO4clima WP2) Jun 9, 2026

bouweandela reviewed Jun 10, 2026

View reviewed changes

		domain definition instead of interpreting the value as an ``MxN`` grid
		specification.

	domain definition instead of interpreting the value as an ``MxN`` grid
	specification.
	domain definition.

		assert target.coord(var_name="rlon") is not None


		def test_update_target_grid_accepts_cordex_domain():

	assert target.coord(var_name="rlat") is not None
	assert target.coords(var_name="rlat")

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