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erikvansebille merged 3 commits into from
Jul 10, 2026
+23 −21
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Updating tutorials that combine fields #2740

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38ed026
Updating tutorials that combine fields
erikvansebille Jul 10, 2026
b071b6d
Update tutorial_manipulating_field_data.ipynb
erikvansebille Jul 10, 2026
fe6dc51
Remove time and depth dimension from field
erikvansebille Jul 10, 2026
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20 changes: 11 additions & 9 deletions docs/user_guide/examples/explanation_kernelloop.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -62,7 +62,7 @@ ds_fields.load() # load the dataset into memory
# Create an idealised wind field and add it to the dataset
tdim, ydim, xdim = (len(ds_fields.time),len(ds_fields.latitude), len(ds_fields.longitude))
ds_fields["UWind"] = xr.DataArray(
data=np.ones((tdim, ydim, xdim)) * np.sin(ds_fields.latitude.values)[None, :, None],
data=0.5 * np.ones((tdim, ydim, xdim)) * np.sin(ds_fields.latitude.values - ds_fields.latitude.values.mean())[None, :, None],
coords=[ds_fields.time, ds_fields.latitude, ds_fields.longitude])

ds_fields["VWind"] = xr.DataArray(
Expand All @@ -88,10 +88,12 @@ fieldset = parcels.FieldSet.from_sgrid_conventions(
Now we define a wind Kernel that uses a forward Euler method to apply the wind forcing. Note that we update the `particles.dx` and `particles.dy` variables, rather than `particles.x` and `particles.y` directly.

```{code-cell}
def wind_kernel(particles, fieldset):
uwind, vwind = fieldset.Wind[particles]
particles.dx += uwind * particles.dt
particles.dy += vwind * particles.dt
def windRK2(particles, fieldset):
(u1, v1) = fieldset.Wind[particles]
x1, y1 = (particles.x + u1 * 0.5 * particles.dt, particles.y + v1 * 0.5 * particles.dt)
(u2, v2) = fieldset.Wind[particles.t + 0.5 * particles.dt, particles.z, y1, x1, particles]
particles.dx += u2 * particles.dt
particles.dy += v2 * particles.dt
```

First run a simulation where we apply Kernels as `[AdvectionRK2, wind_kernel]`
Expand All @@ -100,22 +102,22 @@ First run a simulation where we apply Kernels as `[AdvectionRK2, wind_kernel]`
:tags: [hide-output]
npart = 10
z = np.repeat(ds_fields.depth[0].values, npart)
lons = np.repeat(31, npart)
lons = np.repeat(32.2, npart)
lats = np.linspace(-32.5, -30.5, npart)

pset = parcels.ParticleSet(fieldset, pclass=parcels.Particle, z=z, y=lats, x=lons)
output_file = parcels.ParticleFile(
path="advection_then_wind.parquet", outputdt=np.timedelta64(6,'h')
)
pset.execute(
[parcels.kernels.AdvectionRK2, wind_kernel],
[parcels.kernels.AdvectionRK2, windRK2],
runtime=np.timedelta64(5,'D'),
dt=np.timedelta64(1,'h'),
output_file=output_file,
)
```

Then also run a simulation where we apply the Kernels in the reverse order as `[wind_kernel, AdvectionRK2]`
Then also run a simulation where we apply the Kernels in the reverse order as `[windRK2, AdvectionRK2]`

```{code-cell}
:tags: [hide-output]
Expand All @@ -126,7 +128,7 @@ output_file_reverse = parcels.ParticleFile(
path="wind_then_advection.parquet", outputdt=np.timedelta64(6,"h")
)
pset_reverse.execute(
[wind_kernel, parcels.kernels.AdvectionRK2],
[windRK2, parcels.kernels.AdvectionRK2],
runtime=np.timedelta64(5,"D"),
dt=np.timedelta64(1,"h"),
output_file=output_file_reverse,
Expand Down
24 changes: 12 additions & 12 deletions docs/user_guide/examples/tutorial_manipulating_field_data.ipynb
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Original file line number Diff line number Diff line change
Expand Up @@ -52,19 +52,17 @@
"ds_fields.load() # load the dataset into memory\n",
"\n",
"# Create an idealised wind field and add it to the dataset\n",
"tdim, ydim, xdim = (\n",
" len(ds_fields.time),\n",
" len(ds_fields.latitude),\n",
" len(ds_fields.longitude),\n",
")\n",
"ydim, xdim = len(ds_fields.latitude), len(ds_fields.longitude)\n",
"ds_fields[\"UWind\"] = xr.DataArray(\n",
" data=np.ones((tdim, ydim, xdim)) * np.sin(ds_fields.latitude.values)[None, :, None],\n",
" coords=[ds_fields.time, ds_fields.latitude, ds_fields.longitude],\n",
" data=0.5\n",
" * np.ones((ydim, xdim))\n",
" * np.sin(ds_fields.latitude.values - ds_fields.latitude.values.mean())[:, None],\n",
" coords=[ds_fields.latitude, ds_fields.longitude],\n",
")\n",
"\n",
"ds_fields[\"VWind\"] = xr.DataArray(\n",
" data=np.zeros((tdim, ydim, xdim)),\n",
" coords=[ds_fields.time, ds_fields.latitude, ds_fields.longitude],\n",
" data=np.zeros((ydim, xdim)),\n",
" coords=[ds_fields.latitude, ds_fields.longitude],\n",
")"
]
},
Expand Down Expand Up @@ -126,12 +124,13 @@
"\n",
"npart = 10\n",
"z = np.repeat(ds_fields.depth[0].values, npart)\n",
"lons = np.repeat(31, npart)\n",
"lons = np.repeat(32.2, npart)\n",
"lats = np.linspace(-32.5, -30.5, npart)\n",
"\n",
"pset = parcels.ParticleSet(fieldset, pclass=parcels.Particle, z=z, y=lats, x=lons)\n",
"output_file = parcels.ParticleFile(\n",
" path=\"summed_advection_wind.parquet\", outputdt=np.timedelta64(6, \"h\")\n",
" path=\"summed_advection_wind.parquet\",\n",
" outputdt=np.timedelta64(6, \"h\"),\n",
")\n",
"pset.execute(\n",
" [parcels.kernels.AdvectionRK2],\n",
Expand All @@ -158,8 +157,9 @@
"source": [
"# Plot the resulting particle trajectories overlapped for both cases\n",
"summed_advection_wind = parcels.read_particlefile(\"summed_advection_wind.parquet\")\n",
"fig, ax = plt.subplots(figsize=(5, 3))\n",
"for traj in summed_advection_wind.partition_by(\"particle_id\", maintain_order=True):\n",
" plt.plot(traj[\"x\"], traj[\"y\"], \"-\")\n",
" ax.plot(traj[\"x\"], traj[\"y\"], \"-\")\n",
"plt.show()"
]
}
Expand Down