Expanding explanation of output chunks parameter

docs/examples/tutorial_parcels_structure.ipynb

@@ -395,7 +395,15 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "Note the use of the `chunks` argument in the `pset.ParticleFile()` above. This controls the 'chunking' of the output file, which is a way to optimize the writing of the output file. See also [the advanced output in zarr format tutorial](https://docs.oceanparcels.org/en/latest/examples/documentation_advanced_zarr.html) for more information on this. It is worth to optimise this parameter in your runs, as it can significantly speed up the writing of the output file and thus the runtime of `pset.execution()`."
+    "### A note on output chunking\n",
+    "Note the use of the `chunks` argument in the `pset.ParticleFile()` above. This controls the 'chunking' of the output file, which is a way to optimize the writing of the output file. The default chunking for the output in Parcels is `(number of particles in initial particleset, 1)`. \n",
+    "Note that this default may not be very efficient if \n",
+    "1. you use `repeatdt` to release particles _many_ times during the simulation and/or\n",
+    "2. you expect to output _a lot of timesteps_ (e.g. more than 1000).\n",
+    "\n",
+    "In the first case, it is best to increase the first argument of `chunks`. In the second case, it is best to increase the second argument of `chunks`.\n",
+    "\n",
+    "See also [the advanced output in zarr format tutorial](https://docs.oceanparcels.org/en/latest/examples/documentation_advanced_zarr.html) for more information on this. It is worth to optimise this parameter in your runs, as it can significantly speed up the writing of the output file and thus the runtime of `pset.execution()`."
    ]
   },
   {