erikvansebille · Oct 5, 2026 · Oct 5, 2026 · Oct 6, 2026 · Oct 6, 2026 · Oct 6, 2026
diff --git a/docs/user_guide/convert_croco_3D.ipynb b/docs/user_guide/convert_croco_3D.ipynb
diff --git a/docs/user_guide/fieldsets_grids.ipynb b/docs/user_guide/fieldsets_grids.ipynb
@@ -333,7 +333,7 @@
    "source": [
     "### Vertical coordinates\n",
     "\n",
-    "Lastly, a short note on vertical coordinates. Parcels can handle two styles of vertical coordinates; z-levels which define fixed depth levels in physical space, and sigma-levels which define varying depth levels in physical space as a function of the water column depth. As sigma-levels are effectively \"terrain-following\", the grid cell faces may no longer be orthogonal to the domain surface. The bottom row of Figure 1 visualises these differences, and Parcels handles this all under the hood. See the [CROCO Tutorial](./convert_croco_3D.ipynb) for more details on the sigma-levels implementation.\n"
+    "Lastly, a short note on vertical coordinates. Parcels can handle two styles of vertical coordinates; z-levels which define fixed depth levels in physical space, and sigma-levels which define varying depth levels in physical space as a function of the water column depth. As sigma-levels are effectively \"terrain-following\", the grid cell faces may no longer be orthogonal to the domain surface. The bottom row of Figure 1 visualises these differences, and Parcels handles this all under the hood. See the [Sigma Coordinate Vertical Grids tutorial](./fieldsets_sigma_coordinates.ipynb) for more details on the sigma-levels implementation.\n"
    ]
   }
  ],

diff --git a/docs/user_guide/v4-migration.md b/docs/user_guide/v4-migration.md
@@ -176,10 +176,10 @@ Particle-particle interaction can be <a href="example_interaction.html">performe
 <hr class="migration-divider" />
 
 <div class="migration-bubble migration-change">
-Automatic conversion from depth to sigma grids under the hood is removed
+The Advection_CROCO methods have been removed
 </div>
 <div class="migration-bubble migration-how">
-Explicitly use <code>convert_z_to_sigma_croco</code> in sampling kernels (such as the <code>AdvectionRK4_3D_CROCO</code> or <code>SampleOMegaCroco</code> kernels) when working with <a href="convert_croco_3D">CROCO data</a>
+use the 4-D depth support when working with <a href="convert_croco_3D">CROCO data</a>
 </div>
 <hr class="migration-divider" />
 

diff --git a/pixi.toml b/pixi.toml
@@ -74,6 +74,7 @@ pytest-html = "*"
 pytest-cov = "*"
 pytest-reportlog = "*"
 pytest-timeout = "*"
+xroms = "*"
 
 [feature.test.pypi-dependencies]
 re-assert = "*"
@@ -92,6 +93,7 @@ gsw = "*"
 py-triangle = "*"
 cmocean = "*"
 cartopy = "*"
+xroms = "*"
 xgcm = ">=0.10.0"
 
 [feature.devtools.dependencies]

diff --git a/src/parcels/_datasets/remote.py b/src/parcels/_datasets/remote.py
@@ -119,7 +119,7 @@ def _get_data_home() -> Path:
         "data/SWASH_data/field_0065557.nc",
     ]
     # + [f"data/WOA_data/woa18_decav_t{m:02d}_04.nc" for m in range(1, 13)]
-    + ["data/CROCOidealized_data/CROCO_idealized.nc"]
+    + ["data/CROCOOverflow_data/over_his.nc"]
     # These datasets are from v4 of Parcels where we're opting for Zipped zarr datasets
     + [
         "data-zarr/Benchmarks_FESOM2-baroclinic-gyre/data.zip",
@@ -264,7 +264,7 @@ class _Purpose(enum.Enum):
     # "POPSouthernOcean_data/t.x1_SAMOC_flux.16900*.nc", # TODO v4: In v3 but should not be in v4 https://github.com/Parcels-code/Parcels/issues/2571#issuecomment-4214476973
     # ("SWASH_data/data", (_V3Dataset(_ODIE,"data/SWASH_data/field_00655*.nc"), _Purpose.TUTORIAL)),
     # ("WOA_data/data", (_V3Dataset(_ODIE,"data/WOA_data/woa18_decav_t*_04.nc", _preprocess_set_cf_calendar_360_day), _Purpose.TUTORIAL)),
-    ("CROCOidealized_data/data", (_V3Dataset(_ODIE,"data/CROCOidealized_data/CROCO_idealized.nc"), _Purpose.TUTORIAL)),
+    ("CROCOoverflow_data/data", (_V3Dataset(_ODIE,"data/CROCOOverflow_data/over_his.nc"), _Purpose.TUTORIAL)),
     ("AIFSmeteo/data", (_V3Dataset(_ODIE,"data/AIFS-meteo-data/*.nc"), _Purpose.TUTORIAL))
 ] + [
     ("Benchmarks_FESOM2-baroclinic-gyre/data", (_ZarrZipDataset(_ODIE, 'data-zarr/Benchmarks_FESOM2-baroclinic-gyre/data.zip', zarr_format=2), _Purpose.TESTING)),

diff --git a/src/parcels/_typing.py b/src/parcels/_typing.py
@@ -17,7 +17,7 @@
 from parcels._sgrid.core import Padding
 
 PathLike = str | os.PathLike
-VectorType = Literal["3D", "3DSigma", "2D"] | None  # corresponds with `vector_type`
+VectorType = Literal["3D", "2D"] | None  # corresponds with `vector_type`
 TimeLike = datetime | cftime_datetime | np.datetime64
 
 CfAxisSpatial = Literal["X", "Y", "Z"]

diff --git a/src/parcels/convert.py b/src/parcels/convert.py
@@ -145,7 +145,6 @@ class _ModelConventions:
     varnames_mapping={
         "x_rho": "lon",
         "y_rho": "lat",
-        "s_w": "depth",
     },
 )
 
@@ -605,7 +604,7 @@ def croco_to_sgrid(*, fields: dict[str, xr.Dataset | xr.DataArray], coords: xr.D
                 sgrid.FaceNodePadding("xi_u", "xi_rho", sgrid.Padding.NONE),
                 sgrid.FaceNodePadding("eta_v", "eta_rho", sgrid.Padding.NONE),
             ),
-            vertical_dimensions=(sgrid.FaceNodePadding("s_rho", "depth", sgrid.Padding.NONE),),
+            vertical_dimensions=(sgrid.FaceNodePadding("s_rho", "s_w", sgrid.Padding.NONE),),
         ),
     )
 

diff --git a/src/parcels/kernels/__init__.py b/src/parcels/kernels/__init__.py
@@ -13,11 +13,6 @@
     DiffusionUniformKh,
 )
 from ._integration import RK2, RK4
-from ._sigmagrids import (
-    AdvectionRK2_3D_CROCO,
-    SampleOmegaCroco,
-    convert_z_to_sigma_croco,
-)
 
 __all__ = [  # noqa: RUF022
     # advection
@@ -32,10 +27,6 @@
     "AdvectionDiffusionEM",
     "AdvectionDiffusionM1",
     "DiffusionUniformKh",
-    # sigmagrids
-    "AdvectionRK2_3D_CROCO",
-    "SampleOmegaCroco",
-    "convert_z_to_sigma_croco",
     # integration
     "RK2",
     "RK4",

diff --git a/src/parcels/kernels/_sigmagrids.py b/src/parcels/kernels/_sigmagrids.py
diff --git a/tests/test_convert.py b/tests/test_convert.py
@@ -2,6 +2,7 @@
 import pytest
 import uxarray as ux
 import xarray as xr
+import xroms
 
 import parcels
 import parcels.convert as convert
@@ -116,9 +117,12 @@ def test_convert_mitgcm_offsets():
     assert offsets["Z"] == 0
 
 
+@pytest.mark.xfail(reason="Compatibility issue between xroms v0.6.1 and xgcm v0.10.1")
 def test_convert_croco_offsets():
     ds = datasets_circulation_models["ds_CROCO_idealized"]
     coords = ds[["x_rho", "y_rho", "s_w", "time"]]
+    ds, xgrid = xroms.roms_dataset(ds)
+    ds.xroms.set_grid(xgrid)
 
     ds = convert.croco_to_sgrid(fields={"U": ds["u"], "V": ds["v"]}, coords=coords)
     fieldset = FieldSet.from_sgrid_conventions(ds)

diff --git a/tests/test_sigmagrids.py b/tests/test_sigmagrids.py