style: formating of headers

Author: eni-awowale

intermediate/hierarchicahal_zarr_store.ipynb

@@ -154,7 +154,7 @@
     }
    },
    "source": [
-    "### Chunking\n",
+    "## Chunking\n",
     "Chunking is the process of dividing arrays into smaller pieces, which allows for parallel processing and efficient storage.\n",
     "\n",
     "To examine the chunks in our Zarr store, with `xarray` you can use the `chunks` attribute on the `xr.DataArray` object."
@@ -175,7 +175,7 @@
    "id": "14",
    "metadata": {},
    "source": [
-    "#### Selecting by chunks\n",
+    "### Selecting by chunks\n",
     "\n",
     "Since our underlying data arrays are `dask.Array`, we can access data from each chunked array in our Zarr store. \n",
     "\n",
@@ -204,6 +204,14 @@
     "precip_dt.observed[\"precipitation\"].mean(dim=\"time\")"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "1f7c865c",
+   "metadata": {},
+   "source": [
+    "## Excercise"
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "17",