Changing pset.depth to pset.z throughout code

docs/community/v4-migration.md

@@ -14,6 +14,7 @@ Version 4 of Parcels is unreleased at the moment. The information in this migrat
 - The `time` argument in the Kernel signature has been removed in the Kernel API, so can't be used. Use `particle.time` instead.
 - The `particle` argument in the Kernel signature has been renamed to `particles`.
 - `math` functions should be replaced with array compatible equivalents (e.g., `math.sin` -> `np.sin`). Instead of `ParcelsRandom` you should use numpy's random functions.
+- `particle.depth` has been changed to `particles.z` to be consistent with the [CF conventions for trajectory data](https://cfconventions.org/cf-conventions/cf-conventions.html#trajectory-data), and to make Parcels also generalizable to atmospheric contexts.
 
 ## FieldSet
 

parcels/_core/field.py

@@ -233,7 +233,7 @@ def __getitem__(self, key):
         self._check_velocitysampling()
         try:
             if isinstance(key, KernelParticle):
-                return self.eval(key.time, key.depth, key.lat, key.lon, key)
+                return self.eval(key.time, key.z, key.lat, key.lon, key)
             else:
                 return self.eval(*key)
         except tuple(AllParcelsErrorCodes.keys()) as error:
@@ -334,7 +334,7 @@ def eval(self, time: datetime, z, y, x, particles=None, applyConversion=True):
     def __getitem__(self, key):
         try:
             if isinstance(key, KernelParticle):
-                return self.eval(key.time, key.depth, key.lat, key.lon, key)
+                return self.eval(key.time, key.z, key.lat, key.lon, key)
             else:
                 return self.eval(*key)
         except tuple(AllParcelsErrorCodes.keys()) as error:

parcels/_core/fieldset.py

@@ -240,7 +240,7 @@ def from_copernicusmarine(ds: xr.Dataset):
             if "W" in ds.data_vars:
                 ds["W"] -= ds[
                     "W"
-                ]  # Negate W to convert from up positive to down positive (as that's the direction of positive depth)
+                ]  # Negate W to convert from up positive to down positive (as that's the direction of positive z)
                 fields["W"] = Field("W", ds["W"], grid)
                 fields["UVW"] = VectorField("UVW", fields["U"], fields["V"], fields["W"])
             else:

parcels/_core/kernel.py

@@ -120,11 +120,11 @@ def Setcoords(particles, fieldset):  # pragma: no cover
 
             particles.lon += particles.dlon
             particles.lat += particles.dlat
-            particles.depth += particles.ddepth
+            particles.z += particles.dz
 
             particles.dlon = 0
             particles.dlat = 0
-            particles.ddepth = 0
+            particles.dz = 0
 
             particles.time = particles.time_nextloop
 
@@ -286,6 +286,6 @@ def execute(self, pset, endtime, dt):
                     if error_code == StatusCode.ErrorTimeExtrapolation:
                         error_func(pset[inds].time)
                     else:
-                        error_func(pset[inds].depth, pset[inds].lat, pset[inds].lon)
+                        error_func(pset[inds].z, pset[inds].lat, pset[inds].lon)
 
         return pset

parcels/_core/particle.py

@@ -176,13 +176,13 @@ def get_default_particle(spatial_dtype: np.float32 | np.float64) -> ParticleClas
                 attrs={"standard_name": "latitude", "units": "degrees_north", "axis": "Y"},
             ),
             Variable(
-                "depth",
+                "z",
                 dtype=spatial_dtype,
-                attrs={"standard_name": "depth", "units": "m", "positive": "down"},
+                attrs={"standard_name": "vertical coordinate", "units": "m", "positive": "down"},
             ),
             Variable("dlon", dtype=spatial_dtype, to_write=False),
             Variable("dlat", dtype=spatial_dtype, to_write=False),
-            Variable("ddepth", dtype=spatial_dtype, to_write=False),
+            Variable("dz", dtype=spatial_dtype, to_write=False),
             Variable(
                 "time",
                 dtype=_SAME_AS_FIELDSET_TIME_INTERVAL.VALUE,

parcels/_core/particlefile.py

@@ -126,12 +126,6 @@ def store(self):
     def create_new_zarrfile(self):
         return self._create_new_zarrfile
 
-    def _convert_varout_name(self, var):
-        if var == "depth":
-            return "z"
-        else:
-            return var
-
     def _extend_zarr_dims(self, Z, store, dtype, axis):
         if axis == 1:
             a = np.full((Z.shape[0], self.chunks[1]), _DATATYPES_TO_FILL_VALUES[dtype], dtype=dtype)
@@ -214,8 +208,7 @@ def _write_particle_data(self, *, particle_data, pclass, time_interval, time, in
             obs = np.zeros((self._maxids), dtype=np.int32)
             for var in vars_to_write:
                 dtype = _maybe_convert_time_dtype(var.dtype)
-                varout = self._convert_varout_name(var.name)
-                if varout not in ["trajectory"]:  # because 'trajectory' is written as coordinate
+                if var.name not in ["trajectory"]:  # because 'trajectory' is written as coordinate
                     if var.to_write == "once":
                         data = np.full(
                             (arrsize[0],),
@@ -228,25 +221,24 @@ def _write_particle_data(self, *, particle_data, pclass, time_interval, time, in
                         data = np.full(arrsize, _DATATYPES_TO_FILL_VALUES[dtype], dtype=dtype)
                         data[ids, 0] = particle_data[var.name][indices_to_write]
                         dims = ["trajectory", "obs"]
-                    ds[varout] = xr.DataArray(data=data, dims=dims, attrs=attrs[var.name])
-                    ds[varout].encoding["chunks"] = self.chunks[0] if var.to_write == "once" else self.chunks  # type: ignore[index]
+                    ds[var.name] = xr.DataArray(data=data, dims=dims, attrs=attrs[var.name])
+                    ds[var.name].encoding["chunks"] = self.chunks[0] if var.to_write == "once" else self.chunks  # type: ignore[index]
             ds.to_zarr(store, mode="w")
             self._create_new_zarrfile = False
         else:
             Z = zarr.group(store=store, overwrite=False)
             obs = particle_data["obs_written"][indices_to_write]
             for var in vars_to_write:
                 dtype = _maybe_convert_time_dtype(var.dtype)
-                varout = self._convert_varout_name(var.name)
-                if self._maxids > Z[varout].shape[0]:
-                    self._extend_zarr_dims(Z[varout], store, dtype=dtype, axis=0)
+                if self._maxids > Z[var.name].shape[0]:
+                    self._extend_zarr_dims(Z[var.name], store, dtype=dtype, axis=0)
                 if var.to_write == "once":
                     if len(once_ids) > 0:
-                        Z[varout].vindex[ids_once] = particle_data[var.name][indices_to_write_once]
+                        Z[var.name].vindex[ids_once] = particle_data[var.name][indices_to_write_once]
                 else:
-                    if max(obs) >= Z[varout].shape[1]:  # type: ignore[type-var]
-                        self._extend_zarr_dims(Z[varout], store, dtype=dtype, axis=1)
-                    Z[varout].vindex[ids, obs] = particle_data[var.name][indices_to_write]
+                    if max(obs) >= Z[var.name].shape[1]:  # type: ignore[type-var]
+                        self._extend_zarr_dims(Z[var.name], store, dtype=dtype, axis=1)
+                    Z[var.name].vindex[ids, obs] = particle_data[var.name][indices_to_write]
 
         particle_data["obs_written"][indices_to_write] = obs + 1
 
@@ -262,7 +254,7 @@ def write_latest_locations(self, pset, time):
         time :
             Time at which to write ParticleSet. Note that typically this would be pset.time_nextloop
         """
-        for var in ["lon", "lat", "depth"]:
+        for var in ["lon", "lat", "z"]:
             pset._data[f"{var}"] += pset._data[f"d{var}"]
         pset._data["time"] = pset._data["time_nextloop"]
         self.write(pset, time)

parcels/_core/particleset.py

@@ -39,14 +39,14 @@ class ParticleSet:
         List of initial longitude values for particles
     lat :
         List of initial latitude values for particles
-    depth :
-        Optional list of initial depth values for particles. Default is 0m
+    z :
+        Optional list of initial z values for particles. Default is 0m
     time :
         Optional list of initial time values for particles. Default is fieldset.U.grid.time[0]
     repeatdt : datetime.timedelta or float, optional
         Optional interval on which to repeat the release of the ParticleSet. Either timedelta object, or float in seconds.
-    lonlatdepth_dtype :
-        Floating precision for lon, lat, depth particle coordinates.
+    lonlatz_dtype :
+        Floating precision for lon, lat, z particle coordinates.
         It is either np.float32 or np.float64. Default is np.float32 if fieldset.U.interp_method is 'linear'
         and np.float64 if the interpolation method is 'cgrid_velocity'
     trajectory_ids :
@@ -66,7 +66,7 @@ def __init__(
         pclass=Particle,
         lon=None,
         lat=None,
-        depth=None,
+        z=None,
         time=None,
         trajectory_ids=None,
         **kwargs,
@@ -84,15 +84,15 @@ def __init__(
         if trajectory_ids is None:
             trajectory_ids = np.arange(lon.size)
 
-        if depth is None:
-            mindepth = 0
+        if z is None:
+            minz = 0
             for field in self.fieldset.fields.values():
                 if field.grid.depth is not None:
-                    mindepth = min(mindepth, field.grid.depth[0])
-            depth = np.ones(lon.size) * mindepth
+                    minz = min(minz, field.grid.depth[0])
+            z = np.ones(lon.size) * minz
         else:
-            depth = _convert_to_flat_array(depth)
-        assert lon.size == lat.size and lon.size == depth.size, "lon, lat, depth don't all have the same lenghts"
+            z = _convert_to_flat_array(z)
+        assert lon.size == lat.size and lon.size == z.size, "lon, lat, z don't all have the same lenghts"
 
         if time is None or len(time) == 0:
             # do not set a time yet (because sign_dt not known)
@@ -106,7 +106,7 @@ def __init__(
             raise TypeError("particle time must be a datetime, timedelta, or date object")
         time = np.repeat(time, lon.size) if time.size == 1 else time
 
-        assert lon.size == time.size, "time and positions (lon, lat, depth) do not have the same lengths."
+        assert lon.size == time.size, "time and positions (lon, lat, z) do not have the same lengths."
 
         if fieldset.time_interval:
             _warn_particle_times_outside_fieldset_time_bounds(time, fieldset.time_interval)
@@ -115,7 +115,7 @@ def __init__(
             if kwvar not in ["partition_function"]:
                 kwargs[kwvar] = _convert_to_flat_array(kwargs[kwvar])
                 assert lon.size == kwargs[kwvar].size, (
-                    f"{kwvar} and positions (lon, lat, depth) don't have the same lengths."
+                    f"{kwvar} and positions (lon, lat, z) don't have the same lengths."
                 )
 
         self._data = create_particle_data(
@@ -126,7 +126,7 @@ def __init__(
             initial=dict(
                 lon=lon,
                 lat=lat,
-                depth=depth,
+                z=z,
                 time=time,
                 time_nextloop=time,
                 trajectory=trajectory_ids,
@@ -183,7 +183,7 @@ def __setattr__(self, name, value):
             object.__setattr__(self, name, value)
 
     @staticmethod
-    def lonlatdepth_dtype_from_field_interp_method(field):
+    def lonlatz_dtype_from_field_interp_method(field):
         # TODO update this when now interp methods are implemented
         if field.interp_method == "cgrid_velocity":
             return np.float64
@@ -277,7 +277,7 @@ def _compute_neighbor_tree(self, time, dt):
 
         self._values = np.vstack(
             (
-                self._data["depth"],
+                self._data["z"],
                 self._data["lat"],
                 self._data["lon"],
             )
@@ -306,7 +306,7 @@ def _neighbors_by_coor(self, coor):
     def populate_indices(self):
         """Pre-populate guesses of particle ei (element id) indices"""
         for i, grid in enumerate(self.fieldset.gridset):
-            position = grid.search(self.depth, self.lat, self.lon)
+            position = grid.search(self.z, self.lat, self.lon)
             self._data["ei"][:, i] = grid.ravel_index(
                 {
                     "X": position["X"][0],

parcels/_core/statuscodes.py

@@ -40,7 +40,7 @@ class FieldInterpolationError(RuntimeError):
 
 
 def _raise_field_interpolation_error(z, y, x):
-    raise FieldInterpolationError(f"Field interpolation returned NaN at (depth={z}, lat={y}, lon={x})")
+    raise FieldInterpolationError(f"Field interpolation returned NaN at (z={z}, lat={y}, lon={x})")
 
 
 class FieldOutOfBoundError(RuntimeError):
@@ -50,7 +50,7 @@ class FieldOutOfBoundError(RuntimeError):
 
 
 def _raise_field_out_of_bound_error(z, y, x):
-    raise FieldOutOfBoundError(f"Field sampled out-of-bound, at (depth={z}, lat={y}, lon={x})")
+    raise FieldOutOfBoundError(f"Field sampled out-of-bound, at (z={z}, lat={y}, lon={x})")
 
 
 class FieldOutOfBoundSurfaceError(RuntimeError):
@@ -64,7 +64,7 @@ def format_out(val):
         return "unknown" if val is None else val
 
     raise FieldOutOfBoundSurfaceError(
-        f"Field sampled out-of-bound at the surface, at (depth={format_out(z)}, lat={format_out(y)}, lon={format_out(x)})"
+        f"Field sampled out-of-bound at the surface, at (z={format_out(z)}, lat={format_out(y)}, lon={format_out(x)})"
     )
 
 
@@ -81,7 +81,7 @@ class GridSearchingError(RuntimeError):
 
 
 def _raise_grid_searching_error(z, y, x):
-    raise GridSearchingError(f"Grid searching failed at (depth={z}, lat={y}, lon={x})")
+    raise GridSearchingError(f"Grid searching failed at (z={z}, lat={y}, lon={x})")
 
 
 class GeneralError(RuntimeError):
@@ -91,7 +91,7 @@ class GeneralError(RuntimeError):
 
 
 def _raise_general_error(z, y, x):
-    raise GeneralError(f"General error occurred at (depth={z}, lat={y}, lon={x})")
+    raise GeneralError(f"General error occurred at (z={z}, lat={y}, lon={x})")
 
 
 class TimeExtrapolationError(RuntimeError):

parcels/interpolators.py

@@ -77,18 +77,18 @@ def _get_corner_data_Agrid(
         ti_1 = np.clip(ti + 1, 0, data.shape[0] - 1)
         ti = np.concatenate([np.repeat(ti, lenZ * 4), np.repeat(ti_1, lenZ * 4)])
 
-    # Depth coordinates: 4 points at zi, 4 at zi+1, repeated for both time levels
+    # Z coordinates: 4 points at zi, 4 at zi+1, repeated for both time levels
     if lenZ == 1:
         zi = np.repeat(zi, lenT * 4)
     else:
         zi_1 = np.clip(zi + 1, 0, data.shape[1] - 1)
         zi = np.tile(np.array([zi, zi, zi, zi, zi_1, zi_1, zi_1, zi_1]).flatten(), lenT)
 
-    # Y coordinates: [yi, yi, yi+1, yi+1] for each spatial point, repeated for time/depth
+    # Y coordinates: [yi, yi, yi+1, yi+1] for each spatial point, repeated for time/z
     yi_1 = np.clip(yi + 1, 0, data.shape[2] - 1)
     yi = np.tile(np.repeat(np.column_stack([yi, yi_1]), 2), (lenT) * (lenZ))
 
-    # X coordinates: [xi, xi+1, xi, xi+1] for each spatial point, repeated for time/depth
+    # X coordinates: [xi, xi+1, xi, xi+1] for each spatial point, repeated for time/z
     xi_1 = np.clip(xi + 1, 0, data.shape[3] - 1)
     xi = np.tile(np.column_stack([xi, xi_1, xi, xi_1]).flatten(), (lenT) * (lenZ))
 
@@ -211,17 +211,17 @@ def CGrid_Velocity(
         ti_1 = np.clip(ti + 1, 0, tdim - 1)
         ti_full = np.concatenate([np.repeat(ti, 4), np.repeat(ti_1, 4)])
 
-    # Depth coordinates: 4 points at zi, repeated for both time levels
+    # Z coordinates: 4 points at zi, repeated for both time levels
     zi_full = np.repeat(zi, lenT * 4)
 
-    # Y coordinates: [yi, yi, yi+1, yi+1] for each spatial point, repeated for time/depth
+    # Y coordinates: [yi, yi, yi+1, yi+1] for each spatial point, repeated for time/z
     yi_1 = np.clip(yi + 1, 0, ydim - 1)
     yi_full = np.tile(np.repeat(np.column_stack([yi, yi_1]), 2), (lenT))
     # # TODO check why in some cases minus needed here!!!
     # yi_minus_1 = np.clip(yi - 1, 0, ydim - 1)
     # yi = np.tile(np.repeat(np.column_stack([yi_minus_1, yi]), 2), (lenT))
 
-    # X coordinates: [xi, xi+1, xi, xi+1] for each spatial point, repeated for time/depth
+    # X coordinates: [xi, xi+1, xi, xi+1] for each spatial point, repeated for time/z
     xi_1 = np.clip(xi + 1, 0, xdim - 1)
     xi_full = np.tile(np.column_stack([xi, xi_1, xi, xi_1]).flatten(), (lenT))
 
@@ -313,15 +313,15 @@ def CGrid_Velocity(
             ti_1 = np.clip(ti + 1, 0, tdim - 1)
             ti_full = np.concatenate([np.repeat(ti, 2), np.repeat(ti_1, 2)])
 
-        # Depth coordinates: 1 points at zi, repeated for both time levels
+        # Z coordinates: 1 points at zi, repeated for both time levels
         zi_1 = np.clip(zi + 1, 0, zdim - 1)
         zi_full = np.tile(np.array([zi, zi_1]).flatten(), lenT)
 
-        # Y coordinates: yi+1 for each spatial point, repeated for time/depth
+        # Y coordinates: yi+1 for each spatial point, repeated for time/z
         yi_1 = np.clip(yi + 1, 0, ydim - 1)
         yi_full = np.tile(yi_1, (lenT) * 2)
 
-        # X coordinates: xi+1 for each spatial point, repeated for time/depth
+        # X coordinates: xi+1 for each spatial point, repeated for time/z
         xi_1 = np.clip(xi + 1, 0, xdim - 1)
         xi_full = np.tile(xi_1, (lenT) * 2)