Add case studies document as notebook (#247)

* add case studies document as notebook

* add more case studies

* re-run CI

* fix broken link

Author: j-atkins

docs/user-guide/assignments/case_studies_virtualship.ipynb

@@ -10,4 +10,5 @@ Research_proposal_intro.ipynb
 Research_Proposal_only.ipynb
 sciencecommunication_assignment.ipynb
 Code_of_conduct.ipynb
+case_studies_virtualship.ipynb
 ```

docs/user-guide/assignments/index.md

@@ -0,0 +1,51 @@
+import cartopy.crs as ccrs
+import matplotlib.pyplot as plt
+
+REGIONS = {
+    "Irminger Sea": {"label": "1", "coords": (57.25, -33.0)},
+    "California Current": {"label": "2", "coords": (35, -132)},
+    "Gulf Stream and Deep Western Boundary Current": {
+        "label": "3",
+        "coords": (32.0, -72.0),
+    },
+    "Japan current": {"label": "4", "coords": (31.7, 141)},
+    "Atlantic Meridional Overturning Circulation (AMOC)": {
+        "label": "5",
+        "coords": (26, -47),
+    },
+    "El Niño Southern Oscillation (ENSO)": {"label": "6", "coords": (-5.0, -91.5)},
+    "North Brazil current": {"label": "7", "coords": (2.0, -43.0)},
+    "Somali current": {"label": "8", "coords": (6.0, 53.0)},
+    "East Australian Current": {"label": "9", "coords": (-28.0, 156)},
+    "Drake passage": {"label": "10", "coords": (-58.0, -57.0)},
+    "Agulhas Leakage": {"label": "11", "coords": (-42.0, 15.0)},
+    "Bay of Bengal": {"label": "12", "coords": (11.0, 83.0)},
+    "Brazil-Malvinas Confluence": {"label": "13", "coords": (-35.0, -48.0)},
+    "Cross-shelf exchange on the European North-West Shelf Seas": {
+        "label": "14",
+        "coords": (48.0, -21.0),
+    },
+    "European North-West Shelf Seas": {"label": "15", "coords": (54.0, -3.0)},
+}
+
+
+def _global_plot(width=10, height=5, regions=None) -> None:
+    fig = plt.figure(figsize=(width, height), dpi=300)
+    ax = fig.add_subplot(1, 1, 1, projection=ccrs.Robinson())
+
+    ax.set_global()
+
+    if regions:
+        for _, info in regions.items():
+            ax.text(
+                info["coords"][1],
+                info["coords"][0],
+                info["label"],
+                transform=ccrs.PlateCarree(),
+                fontsize=8,
+                fontweight="bold",
+                color="red",
+            )
+
+    ax.stock_img()
+    ax.coastlines(linewidth=0.5)