Moving the mesh information to the (U)XGrid class

docs/examples/tutorial_stommel_uxarray.ipynb

@@ -88,7 +88,7 @@
     "\n",
     "A `UXArray.Dataset` consists of multiple `UXArray.UxDataArray`'s and a `UXArray.UxGrid`. Parcels views general circulation model data through the `Field` and `VectorField` classes. A `Field` is defined by its `name`, `data`, `grid`, and `interp_method`. A `VectorField` can be constructed by using 2 or 3 `Field`'s. The `Field.data` attribute can be either an `XArray.DataArray` or `UXArray.UxDataArray` object. The `Field.grid` attribute is of type `Parcels.XGrid` or `Parcels.UXGrid`. Last, the `interp_method` is a dynamic function that can be set at runtime to define the interpolation procedure for the `Field`. This gives you the flexibility to use one of the pre-defined interpolation methods included with Parcels v4, or to create your own interpolator. \n",
     "\n",
-    "The first step to creating a `Field` (or `VectorField`) is to define the Grid. For an unstructured grid, we will create a `Parcels.UXGrid` object, which requires a `UxArray.grid` and the vertical layer interface positions."
+    "The first step to creating a `Field` (or `VectorField`) is to define the Grid. For an unstructured grid, we will create a `Parcels.UXGrid` object, which requires a `UxArray.grid` and the vertical layer interface positions. Setting the `mesh` to `\"spherical\"` is a legacy  feature from Parcels v3 that enables unit conversion from `m/s` to `deg/s`; this is needed in this case since the grid locations are defined in units of degrees."
    ]
   },
   {
@@ -99,7 +99,7 @@
    "source": [
     "from parcels.uxgrid import UxGrid\n",
     "\n",
-    "grid = UxGrid(grid=ds.uxgrid, z=ds.coords[\"nz\"])\n",
+    "grid = UxGrid(grid=ds.uxgrid, z=ds.coords[\"nz\"], mesh=\"spherical\")\n",
     "# You can view the uxgrid object with the following command:\n",
     "grid.uxgrid"
    ]
@@ -112,7 +112,7 @@
     "\n",
     "In Parcels, grid searching is conducted with respect to the faces. In other words, when a grid index `ei` is provided to an interpolation method, this refers the face index `fi` at vertical layer `zi` (when unraveled). Within the interpolation method, the `field.grid.uxgrid.face_node_connectivity` attribute can be used to obtain the node indices that surround the face. Using these connectivity tables is necessary for properly indexing node registered data.\n",
     "\n",
-    "For the example Stommel gyre dataset in this tutorial, the `u` and `v` velocity components are face registered (similar to FESOM). Parcels includes a nearest neighbor interpolator for face registered unstructured grid data through `Parcels.application_kernels.interpolation.UXPiecewiseConstantFace`. Below, we create the `Field`s `U` and `V` and associate them with the `UxGrid` we created previously and this interpolation method. Setting the `mesh_type` to `\"spherical\"` is a legacy  feature from Parcels v3 that enables unit conversion from `m/s` to `deg/s`; this is needed in this case since the grid locations are defined in units of degrees."
+    "For the example Stommel gyre dataset in this tutorial, the `u` and `v` velocity components are face registered (similar to FESOM). Parcels includes a nearest neighbor interpolator for face registered unstructured grid data through `Parcels.application_kernels.interpolation.UXPiecewiseConstantFace`. Below, we create the `Field`s `U` and `V` and associate them with the `UxGrid` we created previously and this interpolation method."
    ]
   },
   {
@@ -128,21 +128,18 @@
     "    name=\"U\",\n",
     "    data=ds.U,\n",
     "    grid=grid,\n",
-    "    mesh_type=\"spherical\",\n",
     "    interp_method=UXPiecewiseConstantFace,\n",
     ")\n",
     "V = Field(\n",
     "    name=\"V\",\n",
     "    data=ds.V,\n",
     "    grid=grid,\n",
-    "    mesh_type=\"spherical\",\n",
     "    interp_method=UXPiecewiseConstantFace,\n",
     ")\n",
     "P = Field(\n",
     "    name=\"P\",\n",
     "    data=ds.p,\n",
     "    grid=grid,\n",
-    "    mesh_type=\"spherical\",\n",
     "    interp_method=UXPiecewiseConstantFace,\n",
     ")"
    ]

parcels/_datasets/structured/generated.py

@@ -4,8 +4,8 @@
 import xarray as xr
 
 
-def simple_UV_dataset(dims=(360, 2, 30, 4), maxdepth=1, mesh_type="spherical"):
-    max_lon = 180.0 if mesh_type == "spherical" else 1e6
+def simple_UV_dataset(dims=(360, 2, 30, 4), maxdepth=1, mesh="spherical"):
+    max_lon = 180.0 if mesh == "spherical" else 1e6
 
     return xr.Dataset(
         {"U": (["time", "depth", "YG", "XG"], np.zeros(dims)), "V": (["time", "depth", "YG", "XG"], np.zeros(dims))},

parcels/_index_search.py

@@ -8,6 +8,7 @@
 from parcels._typing import (
     GridIndexingType,
     InterpMethodOption,
+    Mesh,
 )
 from parcels.tools.statuscodes import (
     FieldOutOfBoundError,
@@ -174,7 +175,7 @@ def _search_indices_rectilinear(
         _raise_field_out_of_bound_error(z, y, x)
 
     if field.xdim > 1:
-        if field._mesh_type != "spherical":
+        if field._mesh != "spherical":
             lon_index = field.lon < x
             if lon_index.all():
                 xi = len(field.lon) - 2
@@ -305,7 +306,7 @@ def _search_indices_curvilinear_2d(
         xi = np.where(xsi < -tol, xi - 1, np.where(xsi > 1 + tol, xi + 1, xi))
         yi = np.where(eta < -tol, yi - 1, np.where(eta > 1 + tol, yi + 1, yi))
 
-        (yi, xi) = _reconnect_bnd_indices(yi, xi, grid.ydim, grid.xdim, grid.mesh)
+        (yi, xi) = _reconnect_bnd_indices(yi, xi, grid.ydim, grid.xdim, grid._mesh)
         it += 1
         if it > maxIterSearch:
             print(f"Correct cell not found after {maxIterSearch} iterations")
@@ -408,11 +409,11 @@ def _search_indices_curvilinear(field, time, z, y, x, ti, particle=None, search2
     return (zeta, eta, xsi, zi, yi, xi)
 
 
-def _reconnect_bnd_indices(yi: int, xi: int, ydim: int, xdim: int, sphere_mesh: bool):
-    xi = np.where(xi < 0, (xdim - 2) if sphere_mesh else 0, xi)
-    xi = np.where(xi > xdim - 2, 0 if sphere_mesh else (xdim - 2), xi)
+def _reconnect_bnd_indices(yi: int, xi: int, ydim: int, xdim: int, mesh: Mesh):
+    xi = np.where(xi < 0, (xdim - 2) if mesh == "spherical" else 0, xi)
+    xi = np.where(xi > xdim - 2, 0 if mesh == "spherical" else (xdim - 2), xi)
 
-    xi = np.where(yi > ydim - 2, xdim - xi if sphere_mesh else xi, xi)
+    xi = np.where(yi > ydim - 2, xdim - xi if mesh == "spherical" else xi, xi)
 
     yi = np.where(yi < 0, 0, yi)
     yi = np.where(yi > ydim - 2, ydim - 2, yi)

parcels/field.py

@@ -11,11 +11,7 @@
 
 from parcels._core.utils.time import TimeInterval
 from parcels._reprs import default_repr
-from parcels._typing import (
-    Mesh,
-    VectorType,
-    assert_valid_mesh,
-)
+from parcels._typing import VectorType
 from parcels.application_kernels.interpolation import UXPiecewiseLinearNode, XLinear, ZeroInterpolator
 from parcels.particle import KernelParticle
 from parcels.tools.converters import (
@@ -86,7 +82,7 @@ class Field:
     -----
     The xarray.DataArray or uxarray.UxDataArray object contains the field data and metadata.
         * dims: (time, [nz1 | nz], [face_lat | node_lat | edge_lat], [face_lon | node_lon | edge_lon])
-        * attrs: (location, mesh, mesh_type)
+        * attrs: (location, mesh, mesh)
 
     When using a xarray.DataArray object,
     * The xarray.DataArray object must have the "location" and "mesh" attributes set.
@@ -114,7 +110,6 @@ def __init__(
         name: str,
         data: xr.DataArray | ux.UxDataArray,
         grid: UxGrid | XGrid,
-        mesh_type: Mesh = "flat",
         interp_method: Callable | None = None,
     ):
         if not isinstance(data, (ux.UxDataArray, xr.DataArray)):
@@ -126,8 +121,6 @@ def __init__(
         if not isinstance(grid, (UxGrid, XGrid)):
             raise ValueError(f"Expected `grid` to be a parcels UxGrid, or parcels XGrid object, got {type(grid)}.")
 
-        assert_valid_mesh(mesh_type)
-
         _assert_compatible_combination(data, grid)
 
         if isinstance(grid, XGrid):
@@ -155,8 +148,6 @@ def __init__(
             e.add_note(f"Error validating field {name!r}.")
             raise e
 
-        self._mesh_type = mesh_type
-
         # Setting the interpolation method dynamically
         if interp_method is None:
             self._interp_method = _DEFAULT_INTERPOLATOR_MAPPING[type(self.grid)]
@@ -166,12 +157,10 @@ def __init__(
 
         self.igrid = -1  # Default the grid index to -1
 
-        if self._mesh_type == "flat" or (self.name not in unitconverters_map.keys()):
+        if self.grid._mesh == "flat" or (self.name not in unitconverters_map.keys()):
             self.units = UnitConverter()
-        elif self._mesh_type == "spherical":
+        elif self.grid._mesh == "spherical":
             self.units = unitconverters_map[self.name]
-        else:
-            raise ValueError("Unsupported mesh type in data array attributes. Choose either: 'spherical' or 'flat'")
 
         if self.data.shape[0] > 1:
             if "time" not in self.data.coords:

parcels/kernel.py

@@ -143,7 +143,7 @@ def check_fieldsets_in_kernels(self, pyfunc):  # TODO v4: this can go into anoth
                         stacklevel=2,
                     )
                     self.fieldset.add_constant("RK45_tol", 10)
-                if self.fieldset.U.grid.mesh == "spherical":
+                if self.fieldset.U.grid._mesh == "spherical":
                     self.fieldset.RK45_tol /= (
                         1852 * 60
                     )  # TODO does not account for zonal variation in meter -> degree conversion

parcels/spatialhash.py

@@ -86,7 +86,7 @@ def _hash_index2d(self, coords):
         as the source grid coordinates
         """
         # Wrap longitude to [-180, 180]
-        if self._source_grid.mesh == "spherical":
+        if self._source_grid._mesh == "spherical":
             lon = (coords[:, 1] + 180.0) % (360.0) - 180.0
         else:
             lon = coords[:, 1]

parcels/uxgrid.py

@@ -5,6 +5,7 @@
 import numpy as np
 import uxarray as ux
 
+from parcels._typing import assert_valid_mesh
 from parcels.spatialhash import _barycentric_coordinates
 from parcels.tools.statuscodes import FieldOutOfBoundError
 from parcels.xgrid import _search_1d_array
@@ -20,7 +21,7 @@ class UxGrid(BaseGrid):
     for interpolation on unstructured grids.
     """
 
-    def __init__(self, grid: ux.grid.Grid, z: ux.UxDataArray) -> UxGrid:
+    def __init__(self, grid: ux.grid.Grid, z: ux.UxDataArray, mesh="flat") -> UxGrid:
         """
         Initializes the UxGrid with a uxarray grid and vertical coordinate array.
 
@@ -32,13 +33,18 @@ def __init__(self, grid: ux.grid.Grid, z: ux.UxDataArray) -> UxGrid:
             A 1D array of vertical coordinates (depths) associated with the layer interface heights (not the mid-layer depths).
             While uxarray allows nz to be spatially and temporally varying, the parcels.UxGrid class considers the case where
             the vertical coordinate is constant in time and space. This implies flat bottom topography and no moving ALE vertical grid.
+        mesh : str, optional
+            The type of mesh used for the grid. Either "flat" (default) or "spherical".
         """
         self.uxgrid = grid
         if not isinstance(z, ux.UxDataArray):
             raise TypeError("z must be an instance of ux.UxDataArray")
         if z.ndim != 1:
             raise ValueError("z must be a 1D array of vertical coordinates")
         self.z = z
+        self._mesh = mesh
+
+        assert_valid_mesh(mesh)
 
     @property
     def depth(self):

parcels/xgrid.py

@@ -8,6 +8,7 @@
 
 from parcels import xgcm
 from parcels._index_search import _search_indices_curvilinear_2d
+from parcels._typing import assert_valid_mesh
 from parcels.basegrid import BaseGrid
 from parcels.spatialhash import SpatialHash
 
@@ -97,13 +98,15 @@ class XGrid(BaseGrid):
 
     def __init__(self, grid: xgcm.Grid, mesh="flat"):
         self.xgcm_grid = grid
-        self.mesh = mesh
+        self._mesh = mesh
         self._spatialhash = None
         ds = grid._ds
 
         if len(set(grid.axes) & {"X", "Y", "Z"}) > 0:  # Only if spatial grid is >0D (see #2054 for further development)
             assert_valid_lat_lon(ds["lat"], ds["lon"], grid.axes)
 
+        assert_valid_mesh(mesh)
+
     @classmethod
     def from_dataset(cls, ds: xr.Dataset, mesh="flat", xgcm_kwargs=None):
         """WARNING: unstable API, subject to change in future versions."""  # TODO v4: make private or remove warning on v4 release

tests/utils.py

@@ -68,15 +68,15 @@ def create_fieldset_global(xdim=200, ydim=100):
     return FieldSet.from_data(data, dimensions, mesh="flat")
 
 
-def create_fieldset_zeros_conversion(mesh_type="spherical", xdim=200, ydim=100) -> FieldSet:
+def create_fieldset_zeros_conversion(mesh="spherical", xdim=200, ydim=100) -> FieldSet:
     """Zero velocity field with lat and lon determined by a conversion factor."""
-    mesh_conversion = 1 / 1852.0 / 60 if mesh_type == "spherical" else 1
-    ds = simple_UV_dataset(dims=(2, 1, ydim, xdim), mesh_type=mesh_type)
+    mesh_conversion = 1 / 1852.0 / 60 if mesh == "spherical" else 1
+    ds = simple_UV_dataset(dims=(2, 1, ydim, xdim), mesh=mesh)
     ds["lon"].data = np.linspace(-1e6 * mesh_conversion, 1e6 * mesh_conversion, xdim)
     ds["lat"].data = np.linspace(-1e6 * mesh_conversion, 1e6 * mesh_conversion, ydim)
-    grid = XGrid.from_dataset(ds)
-    U = Field("U", ds["U"], grid, mesh_type=mesh_type, interp_method=XLinear)
-    V = Field("V", ds["V"], grid, mesh_type=mesh_type, interp_method=XLinear)
+    grid = XGrid.from_dataset(ds, mesh=mesh)
+    U = Field("U", ds["U"], grid, interp_method=XLinear)
+    V = Field("V", ds["V"], grid, interp_method=XLinear)
 
     UV = VectorField("UV", U, V)
     return FieldSet([U, V, UV])

tests/v4/test_advection.py

@@ -32,21 +32,21 @@
 }
 
 
-@pytest.mark.parametrize("mesh_type", ["spherical", "flat"])
-def test_advection_zonal(mesh_type, npart=10):
+@pytest.mark.parametrize("mesh", ["spherical", "flat"])
+def test_advection_zonal(mesh, npart=10):
     """Particles at high latitude move geographically faster due to the pole correction in `GeographicPolar`."""
-    ds = simple_UV_dataset(mesh_type=mesh_type)
+    ds = simple_UV_dataset(mesh=mesh)
     ds["U"].data[:] = 1.0
-    grid = XGrid.from_dataset(ds)
-    U = Field("U", ds["U"], grid, mesh_type=mesh_type, interp_method=XLinear)
-    V = Field("V", ds["V"], grid, mesh_type=mesh_type, interp_method=XLinear)
+    grid = XGrid.from_dataset(ds, mesh=mesh)
+    U = Field("U", ds["U"], grid, interp_method=XLinear)
+    V = Field("V", ds["V"], grid, interp_method=XLinear)
     UV = VectorField("UV", U, V)
     fieldset = FieldSet([U, V, UV])
 
     pset = ParticleSet(fieldset, lon=np.zeros(npart) + 20.0, lat=np.linspace(0, 80, npart))
     pset.execute(AdvectionRK4, runtime=np.timedelta64(2, "h"), dt=np.timedelta64(15, "m"))
 
-    if mesh_type == "spherical":
+    if mesh == "spherical":
         assert (np.diff(pset.lon) > 1.0e-4).all()
     else:
         assert (np.diff(pset.lon) < 1.0e-4).all()
@@ -58,7 +58,7 @@ def periodicBC(particle, fieldset, time):
 
 
 def test_advection_zonal_periodic():
-    ds = simple_UV_dataset(dims=(2, 2, 2, 2), mesh_type="flat")
+    ds = simple_UV_dataset(dims=(2, 2, 2, 2), mesh="flat")
     ds["U"].data[:] = 0.1
     ds["lon"].data = np.array([0, 2])
     ds["lat"].data = np.array([0, 2])
@@ -86,7 +86,7 @@ def test_advection_zonal_periodic():
 
 def test_horizontal_advection_in_3D_flow(npart=10):
     """Flat 2D zonal flow that increases linearly with depth from 0 m/s to 1 m/s."""
-    ds = simple_UV_dataset(mesh_type="flat")
+    ds = simple_UV_dataset(mesh="flat")
     ds["U"].data[:] = 1.0
     grid = XGrid.from_dataset(ds)
     U = Field("U", ds["U"], grid, interp_method=XLinear)
@@ -105,7 +105,7 @@ def test_horizontal_advection_in_3D_flow(npart=10):
 @pytest.mark.parametrize("direction", ["up", "down"])
 @pytest.mark.parametrize("wErrorThroughSurface", [True, False])
 def test_advection_3D_outofbounds(direction, wErrorThroughSurface):
-    ds = simple_UV_dataset(mesh_type="flat")
+    ds = simple_UV_dataset(mesh="flat")
     grid = XGrid.from_dataset(ds)
     U = Field("U", ds["U"], grid, interp_method=XLinear)
     U.data[:] = 0.01  # Set U to small value (to avoid horizontal out of bounds)
@@ -208,9 +208,9 @@ def test_length1dimensions(u, v, w):  # TODO: Refactor this test to be more read
 
 def test_radialrotation(npart=10):
     ds = radial_rotation_dataset()
-    grid = XGrid.from_dataset(ds)
-    U = parcels.Field("U", ds["U"], grid, mesh_type="flat", interp_method=XLinear)
-    V = parcels.Field("V", ds["V"], grid, mesh_type="flat", interp_method=XLinear)
+    grid = XGrid.from_dataset(ds, mesh="flat")
+    U = parcels.Field("U", ds["U"], grid, interp_method=XLinear)
+    V = parcels.Field("V", ds["V"], grid, interp_method=XLinear)
     UV = parcels.VectorField("UV", U, V)
     fieldset = parcels.FieldSet([U, V, UV])