Remove 'mesh' arg from add_constant_field

docs/user_guide/examples/tutorial_diffusion.ipynb

@@ -84,7 +84,7 @@
     "\n",
     "The advection component of these kernels is similar to that of the Explicit Euler advection kernel (`AdvectionEE`). In the special case where diffusivity is constant over the entire domain, the diffusion-only kernel {py:func}`parcels.kernels.DiffusionUniformKh` can be used in combination with an advection kernel of choice. Since the diffusivity here is space-independent, gradients are not calculated, increasing efficiency. The diffusion-step can in this case be computed after or before advection, thus allowing you to chain kernels in a list.\n",
     "\n",
-    "Just like velocities, diffusivities are passed to Parcels in the form of {py:func}`parcels.Field` objects. When using {py:func}`parcels.kernels.DiffusionUniformKh`, they should be added to the {py:func}`parcels.FieldSet` object as constant fields, e.g. `fieldset.add_constant_field(\"Kh_zonal\", 1, mesh=\"flat\")`.\n",
+    "Just like velocities, diffusivities are passed to Parcels in the form of {py:func}`parcels.Field` objects. When using {py:func}`parcels.kernels.DiffusionUniformKh`, they should be added to the {py:func}`parcels.FieldSet` object as constant fields, e.g. `fieldset.add_constant_field(\"Kh_zonal\", 1)`.\n",
     "\n",
     "To make a central difference approximation for computing the gradient in diffusivity, a resolution for this approximation `dres` is needed: _Parcels_ approximates the gradients in diffusivities by using their values at the particle's location ± `dres` (in both $x$ and $y$). A value of `dres` must be specified and added to the FieldSet by the user (e.g. `fieldset.add_context(\"dres\", 0.01)`). Currently, it is unclear what the best value of `dres` is. From experience, the size of `dres` should be smaller than the spatial resolution of the data, but within reasonable limits of machine precision to avoid numerical errors. We are working on a method to compute gradients differently so that specifying `dres` is not necessary anymore.\n",
     "\n",
@@ -203,7 +203,7 @@
    "outputs": [],
    "source": [
     "fieldset = parcels.FieldSet.from_sgrid_conventions(ds, mesh=\"flat\")\n",
-    "fieldset.add_constant_field(\"Kh_zonal\", 1, mesh=\"flat\")\n",
+    "fieldset.add_constant_field(\"Kh_zonal\", 1)\n",
     "fieldset.add_context(\"dres\", 0.00005)"
    ]
   },

docs/user_guide/examples/tutorial_interaction.ipynb

@@ -101,8 +101,8 @@
     "    \"\"\"Define a fieldset with only diffusion\"\"\"\n",
     "    ds = simple_UV_dataset(dims=(1, 1, 1, 1), mesh=\"flat\")\n",
     "    fieldset = parcels.FieldSet.from_sgrid_conventions(ds, mesh=\"flat\")\n",
-    "    fieldset.add_constant_field(\"Kh_zonal\", 0.0005, mesh=\"flat\")\n",
-    "    fieldset.add_constant_field(\"Kh_meridional\", 0.0005, mesh=\"flat\")\n",
+    "    fieldset.add_constant_field(\"Kh_zonal\", 0.0005)\n",
+    "    fieldset.add_constant_field(\"Kh_meridional\", 0.0005)\n",
     "    return fieldset"
    ]
   },
@@ -361,7 +361,7 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Parcels:docs (3.14.6)",
+   "display_name": "default",
    "language": "python",
    "name": "python3"
   },
@@ -375,7 +375,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.14.6"
+   "version": "3.14.7"
   }
  },
  "nbformat": 4,

docs/user_guide/examples/tutorial_stuck_particles.ipynb

@@ -821,8 +821,8 @@
     "fieldset = parcels.FieldSet.from_sgrid_conventions(ds_fset)\n",
     "fieldset = fieldset.to_windowed_arrays()\n",
     "\n",
-    "fieldset.add_constant_field(\"Kh_zonal\", 5, mesh=\"spherical\")\n",
-    "fieldset.add_constant_field(\"Kh_meridional\", 5, mesh=\"spherical\")\n",
+    "fieldset.add_constant_field(\"Kh_zonal\", 5)\n",
+    "fieldset.add_constant_field(\"Kh_meridional\", 5)\n",
     "fieldset.add_context(\"dres\", 0.083)\n",
     "\n",
     "npart = 10  # number of particles to be released\n",

src/parcels/_core/fieldset.py

@@ -191,7 +191,7 @@ def to_windowed_arrays(self, *, max_levels: int | None = None):
             model.to_windowed_arrays(max_levels=max_levels)
         return self
 
-    def add_constant_field(self, name: str, value, mesh: ptyping.TMesh = "spherical"):
+    def add_constant_field(self, name: str, value):
         """Wrapper function to add a Field that is constant in space,
            useful e.g. when using constant horizontal diffusivity
 
@@ -201,18 +201,9 @@ def add_constant_field(self, name: str, value, mesh: ptyping.TMesh = "spherical"
             Name of the :class:`parcels.field.Field` object to be added
         value :
             Value of the constant field
-        mesh : str
-            String indicating the type of mesh coordinates,
-
-            1. spherical (default): Lat and lon in degree, with a
-               correction for zonal velocity U near the poles.
-            2. flat: No conversion, lat/lon are assumed to be in m.
         """
-        if mesh not in ("flat", "spherical"):
-            raise ValueError(f"mesh must be one of ['flat', 'spherical']. Got {mesh!r}.")
-
         if self.constant_model is None:
-            self.constant_model = create_empty_constant_field_model(mesh)
+            self.constant_model = create_empty_constant_field_model(self.mesh)
 
         self.constant_model.data[name] = (["time", "depth", "lat", "lon"], np.full((1, 1, 1, 1), value))
 

src/parcels/_core/model.py

@@ -296,8 +296,9 @@ def assert_vector_field_components_in_dataset(ds: xr.Dataset, vector_fields: pty
     return
 
 
-def create_empty_constant_field_model(mesh: ptyping.TMesh) -> StructuredModelData:
+def create_empty_constant_field_model(mesh: SphericalMesh | FlatMesh) -> StructuredModelData:
     """Create a empty model for constant fields with the given mesh type."""
+    mesh_: ptyping.TMesh = "flat" if isinstance(mesh, FlatMesh) else mesh
     return StructuredModelData.from_sgrid_conventions(
         xr.Dataset(
             {},
@@ -319,7 +320,7 @@ def create_empty_constant_field_model(mesh: ptyping.TMesh) -> StructuredModelDat
                 ),
             ),
         ),
-        mesh=mesh,
+        mesh=mesh_,
         vector_fields={},
     )
 

src/parcels/kernels/_advectiondiffusion.py

@@ -122,9 +122,9 @@ def DiffusionUniformKh(particles, fieldset):  # pragma: no cover
 
     Assumes that fieldset has constant fields `Kh_zonal` and `Kh_meridional`.
     These can be added via e.g.
-    `fieldset.add_constant_field("Kh_zonal", kh_zonal, mesh=mesh)`
+    `fieldset.add_constant_field("Kh_zonal", kh_zonal)`
     or
-    `fieldset.add_constant_field("Kh_meridional", kh_meridional, mesh=mesh)`
+    `fieldset.add_constant_field("Kh_meridional", kh_meridional)`
     where mesh is either 'flat' or 'spherical'
 
     This kernel assumes diffusivity gradients are zero and is therefore more efficient.

tests/test_diffusion.py

@@ -26,8 +26,8 @@ def test_fieldKh_Brownian(mesh):
     ds["lon"].data = np.array([-1e6, 1e6])
     ds["lat"].data = np.array([-1e6, 1e6])
     fieldset = FieldSet.from_sgrid_conventions(ds, mesh=mesh)
-    fieldset.add_constant_field("Kh_zonal", kh_zonal, mesh=mesh)
-    fieldset.add_constant_field("Kh_meridional", kh_meridional, mesh=mesh)
+    fieldset.add_constant_field("Kh_zonal", kh_zonal)
+    fieldset.add_constant_field("Kh_meridional", kh_meridional)
 
     npart = 100
     runtime = np.timedelta64(2, "h")

tests/test_fieldset.py

@@ -33,7 +33,7 @@ def fieldset_two_models():
     fset2 = FieldSet.from_sgrid_conventions(ds2, mesh="flat", vector_fields={"UV_wind": ("U_wind", "V_wind")})
     fset2.add_context("my_value", 2.0)
     fset2.add_context("my_list", [1, 2, "hello"])
-    fset2.add_constant_field("constant_field", 3.0, mesh="flat")
+    fset2.add_constant_field("constant_field", 3.0)
     return fset1 + fset2
 
 
@@ -74,7 +74,7 @@ def test_fieldset_add_context_invalid_name(fieldset, name):
 
 
 def test_fieldset_add_constant_field(fieldset):
-    fieldset.add_constant_field("test_constant_field", 1.0, mesh="flat")
+    fieldset.add_constant_field("test_constant_field", 1.0)
 
     # Get a point in the domain
     time = ds["time"].mean()
@@ -91,7 +91,7 @@ def test_fieldset_gridset(fieldset):
     assert fieldset.fields["UV"].grid in fieldset.gridset
     assert len(fieldset.gridset) == 1
 
-    fieldset.add_constant_field("constant_field", 1.0, mesh="flat")
+    fieldset.add_constant_field("constant_field", 1.0)
     assert len(fieldset.gridset) == 2
 
 
@@ -238,7 +238,7 @@ def test_multi_model_time_interval():
     ds3["time"] = (ds3["time"].dims, ds3["time"].data + np.timedelta64(timedelta(days=2)), ds3["time"].attrs)
     fieldset += FieldSet.from_sgrid_conventions(ds3, mesh="flat")
 
-    fieldset.add_constant_field("constant_field", 1.0, mesh="flat")
+    fieldset.add_constant_field("constant_field", 1.0)
 
     assert len(fieldset.models) == 3
     assert fieldset.constant_model is not None
@@ -258,7 +258,7 @@ def test_multi_model_nonoverlapping_time_interval():
     ds3["time"] = (ds3["time"].dims, ds3["time"].data + np.timedelta64(timedelta(days=2000)), ds3["time"].attrs)
     fieldset += FieldSet.from_sgrid_conventions(ds3, mesh="flat")
 
-    fieldset.add_constant_field("constant_field", 1.0, mesh="flat")
+    fieldset.add_constant_field("constant_field", 1.0)
 
     assert len(fieldset.models) == 3
     assert fieldset.constant_model is not None