fix writing suggestions

Author: reint-fischer

docs/user_guide/examples/explanation_interpolation.md

@@ -12,9 +12,23 @@ we _evaluate_ the `parcels.Field` at the particles real position in time and spa
 In Parcels we can do this using square brackets:
 
 ```
-particles.temperature = fieldset.temperature[particles.time, particles.z, particles.lat, particles.lon]
+particles.temperature = fieldset.temperature[particles]
 ```
 
+````{note}
+The statement above is shorthand for 
+```python
+particles.temperature = fieldset.temperature[particles.time, particles.z, particles.lat, particles.lon, particles]
+```
+where the `particles` argument at the end provides the grid search algorithm with a first guess for the element indices to interpolate on. 
+
+If you want to sample at a different location, or time, that is not necessarily close to the particles location, you can use
+```python
+particles.temperature = fieldset.temperature[time, depth, lat, lon]
+```
+but this could be slower for curvilinear and unstructured because the entire grid needs to be searched.
+````
+
 The values of the `temperature` field at the particles' positions are determined using an interpolation
 method. This interpolation method defines how the discretized values of the `parcels.Field` should
 relate to the value at any point within a grid cell.

docs/user_guide/examples/tutorial_interpolation.ipynb

@@ -6,7 +6,7 @@
    "metadata": {},
    "source": [
     "# Using `parcels.interpolators`\n",
-    "Parcels comes with a number of different interpolation methods for tracer fields, such as temperature. Here, we will look at a few common `parcels.interpolators` for structured (`X`) grids, and how to configure them in an idealised example. For more guidance on the sampling of such fields, check out the [sampling guide](./tutorial_sampling).\n",
+    "Parcels comes with a number of different interpolation methods for tracer fields, such as temperature. Here, we will look at a few common `parcels.interpolators` for structured (`X`) grids, and how to configure them in an idealised example. For more guidance on the sampling of such fields, check out the [sampling tutorial](./tutorial_sampling).\n",
     "\n",
     "We first import the relevant modules"
    ]
@@ -29,7 +29,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "We create a small 2D structured grid where `P` is a tracer that we want to interpolate. In each grid cell, `P` has a random value between 0.1 and 1.1. We then set `P[1,1]` to `0`, which for Parcels specifies that this is a land cell\n"
+    "We create a small 2D structured grid, where `P` is a tracer that we want to interpolate. In each grid cell, `P` has a random value between 0.1 and 1.1. We then set `P[1,1]` to `0`, which for Parcels specifies that this is a land cell\n"
    ]
   },
   {
@@ -256,7 +256,7 @@
    "metadata": {},
    "source": [
     "## Interpolation at boundaries\n",
-    "In some cases we need to implement specific boundary conditions, for example to prevent particles from \n",
+    "In some cases, we need to implement specific boundary conditions, for example to prevent particles from \n",
     "getting \"stuck\" near land. [This guide](../examples_v3/documentation_unstuck_Agrid.ipynb) describes \n",
     "how to implement this in parcels using `parcels.interpolators.XFreeslip` and `parcels.interpolators.XPartialslip`."
    ]
@@ -266,7 +266,7 @@
    "metadata": {},
    "source": [
     "## Write your own interpolator\n",
-    "The interpolators included in Parcels are designed for common interpolation schemes in Parcels simulations. If we want to add a custom interpolation method, we can write our own interpolator function (e.g. spline) using the [interpolator API](./explanation_interpolation.md#interpolator-api)."
+    "The interpolators included in Parcels are designed for common interpolation schemes in Parcels simulations. If we want to add a custom interpolation method, we can write a custom function (e.g. spline) using the [interpolator API](./explanation_interpolation.md#interpolator-api)."
    ]
   }
  ],