Updating explanation in interpolation tutorial

Author: erikvansebille

docs/user_guide/examples/tutorial_interpolation.ipynb

@@ -59,7 +59,9 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "From this dataset we create a {py:obj}`parcels.FieldSet` using the {py:meth}`parcels.FieldSet.from_sgrid_conventions` constructor, which automatically sets up the grid and fields according to Parcels' s-grid conventions."
+    "From this dataset we create a {py:obj}`parcels.FieldSet` using the {py:meth}`parcels.FieldSet.from_sgrid_conventions` constructor, which automatically sets up the grid and fields according to Parcels' s-grid conventions.\n",
+    "\n",
+    "The default interpolator for fields on structured A-grid grids is (tri)linear interpolation, implemented in `parcels.interpolators.XLinear`."
    ]
   },
   {
@@ -68,7 +70,9 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "fieldset = parcels.FieldSet.from_sgrid_conventions(ds, mesh=\"flat\")"
+    "fieldset = parcels.FieldSet.from_sgrid_conventions(ds, mesh=\"flat\")\n",
+    "\n",
+    "assert fieldset.P.interp_method == parcels.interpolators.XLinear"
    ]
   },
   {