Add text to swash notebook

Author: erikvansebille

docs/user_guide/examples/tutorial_swash.ipynb

@@ -8,10 +8,18 @@
     "# 🖥️ SWASH tutorial"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "1",
+   "metadata": {},
+   "source": [
+    "This tutorial shows how to load in native Matlab files from the SWASH model and convert them to a Parcels-compatible `FieldSet`. The tutorial also shows how to run a simple particle tracking simulation using the SWASH data."
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,
-   "id": "1",
+   "id": "2",
    "metadata": {},
    "outputs": [],
    "source": [
@@ -25,31 +33,50 @@
   {
    "cell_type": "code",
    "execution_count": null,
-   "id": "2",
+   "id": "3",
    "metadata": {},
    "outputs": [],
    "source": [
-    "swash_files = parcels.tutorial.open_dataset(\"SWASH_data/data\", download_only=True)"
+    "data_file, coord_file = parcels.tutorial.open_dataset(\n",
+    "    \"SWASH_data/data\", download_only=True\n",
+    ")\n",
+    "print(data_file, coord_file)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "4",
+   "metadata": {},
+   "source": [
+    "Unlike the other tutorials, this tutorial uses the original SWASH output files in Matlab format. If you want to use your own SWASH output files, you should use the `GRD.mat` and `ALL.mat` files in the `parcels.convert.swash_to_sgrid()` function below."
    ]
   },
   {
    "cell_type": "code",
    "execution_count": null,
-   "id": "3",
+   "id": "5",
    "metadata": {},
    "outputs": [],
    "source": [
     "ds = parcels.convert.swash_to_sgrid(\n",
-    "    data_file=swash_files[0], coord_file=swash_files[1], total_depth=8.0\n",
+    "    data_file=data_file, coord_file=coord_file, total_depth=8.0\n",
     ")\n",
     "fieldset = parcels.FieldSet.from_sgrid_conventions(ds)\n",
     "fieldset.describe()"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "6",
+   "metadata": {},
+   "source": [
+    "Now, we can use this `FieldSet` to run a simulation (note it's very short because the dataset provided in this tutorial is only 20 seconds long)."
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,
-   "id": "4",
+   "id": "7",
    "metadata": {},
    "outputs": [],
    "source": [
@@ -73,10 +100,18 @@
     ")"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "8",
+   "metadata": {},
+   "source": [
+    "And then plot the results of the simulation, along with the water level at a given time step. The starting positions of the particles are also shown in white."
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,
-   "id": "5",
+   "id": "9",
    "metadata": {},
    "outputs": [],
    "source": [
@@ -90,12 +125,6 @@
     "ax.set_xlim([14, 16])\n",
     "plt.show()"
    ]
-  },
-  {
-   "cell_type": "markdown",
-   "id": "6",
-   "metadata": {},
-   "source": []
   }
  ],
  "metadata": {