Testing offsets on mitgcm example data

Author: erikvansebille

src/parcels/convert.py

@@ -45,9 +45,11 @@
 _MITGCM_AXIS_VARNAMES = {
     "XC": "X",
     "XG": "X",
+    "Xp1": "X",
     "lon": "X",
     "YC": "Y",
     "YG": "Y",
+    "Yp1": "Y",
     "lat": "Y",
     "Zu": "Z",
     "Zl": "Z",
@@ -330,7 +332,7 @@ def mitgcm_to_sgrid(*, fields: dict[str, xr.Dataset | xr.DataArray], coords: xr.
     ds.attrs.clear()  # Clear global attributes from the merging
 
     ds = _maybe_rename_variables(ds, _MITGCM_VARNAMES_MAPPING)
-    # ds = _set_axis_attrs(ds, _MITGCM_AXIS_VARNAMES)
+    ds = _set_axis_attrs(ds, _MITGCM_AXIS_VARNAMES)
     ds = _maybe_swap_depth_direction(ds)
 
     if "grid" in ds.cf.cf_roles:

tests/test_convert.py

@@ -6,6 +6,7 @@
 from parcels import FieldSet
 from parcels._core.utils import sgrid
 from parcels._datasets.structured.circulation_models import datasets as datasets_circulation_models
+from parcels.interpolators._xinterpolators import _get_offsets_dictionary
 
 
 def test_nemo_to_sgrid():
@@ -39,6 +40,18 @@ def test_nemo_to_sgrid():
     }.issubset(set(ds["V"].dims))
 
 
+def test_convert_mitgcm_offsets():
+    data_folder = parcels.download_example_dataset("MITgcm_example_data")
+    ds_fields = xr.open_dataset(data_folder / "mitgcm_UV_surface_zonally_reentrant.nc")
+    coords = ds_fields[["XG", "YG", "Zl", "time"]]
+    ds_fset = convert.mitgcm_to_sgrid(fields={"U": ds_fields.UVEL, "V": ds_fields.VVEL}, coords=coords)
+    fieldset = FieldSet.from_sgrid_conventions(ds_fset)
+    offsets = _get_offsets_dictionary(fieldset.UV.grid)
+    assert offsets["X"] == 0
+    assert offsets["Y"] == 0
+    assert offsets["Z"] == 0
+
+
 _COPERNICUS_DATASETS = [
     datasets_circulation_models["ds_copernicusmarine"],
     datasets_circulation_models["ds_copernicusmarine_waves"],