Add support for staggered variables on B-grid

Author: dougiesquire

src/access_moppy/ocean.py

@@ -190,10 +190,12 @@ def __init__(
         self.arakawa = "B"  # ACCESS-OM2 MOM5 uses B-grid
 
     def infer_grid_type(self):
-        """Infer the grid type (T, U, V, Q) and memory mode based on present coordinates."""
+        """Infer the grid type (T, U, V, C) and memory mode based on present coordinates."""
         grid_types = {
             "T": {"xt_ocean", "yt_ocean"},
-            "U": {"xu_ocean", "yu_ocean"},
+            "U": {"xu_ocean", "yt_ocean"},
+            "V": {"xt_ocean", "yu_ocean"},
+            "C": {"xu_ocean", "yu_ocean"},
         }
         present_coords = set(self.ds.coords)
 
@@ -246,7 +248,7 @@ def __init__(
         self.arakawa = "C"  # ACCESS-OM3 MOM6 uses C-grid
 
     def infer_grid_type(self):
-        """Infer the grid type (T, U, V, Q) and memory mode based on present coordinates."""
+        """Infer the grid type (T, U, V, C) and memory mode based on present coordinates."""
         grid_types = {
             "T": {"xh", "yh"},
             "U": {"xq", "yh"},

src/access_moppy/ocean_supergrid.py

@@ -238,14 +238,24 @@ def extract_grid(self, grid_type: str, arakawa: str, symmetric=None):
             case "B":
                 match grid_type:
                     case "T":
-                        x_centers = self.hcell_centres_x
+                        x_centers = self.hcell_centres_x  # geolon_t
                         x_bounds = self.hcell_corners_x
-                        y_centers = self.hcell_centres_y
+                        y_centers = self.hcell_centres_y  # geolat_t
                         y_bounds = self.hcell_corners_y
                     case "U":
-                        x_centers = self.qcell_centres_x[1:, 1:]
+                        x_centers = self.qcell_centres_x[1:, 1:]  # geolon_c
                         x_bounds = self.qcell_corners_x[1:, 1:, :]
-                        y_centers = self.qcell_centres_y[1:, 1:]
+                        y_centers = self.hcell_centres_y  # geolat_t
+                        y_bounds = self.hcell_corners_y
+                    case "V":
+                        x_centers = self.hcell_centres_x  # geolon_t
+                        x_bounds = self.hcell_corners_x
+                        y_centers = self.qcell_centres_y[1:, 1:]  # geolat_c
+                        y_bounds = self.qcell_corners_y[1:, 1:, :]
+                    case "C":
+                        x_centers = self.qcell_centres_x[1:, 1:]  # geolon_c
+                        x_bounds = self.qcell_corners_x[1:, 1:, :]
+                        y_centers = self.qcell_centres_y[1:, 1:]  # geolat_c
                         y_bounds = self.qcell_corners_y[1:, 1:, :]
                     case _:
                         raise ValueError(
@@ -255,24 +265,24 @@ def extract_grid(self, grid_type: str, arakawa: str, symmetric=None):
                 i_start = 0 if symmetric else 1
                 match grid_type:
                     case "T":
-                        x_centers = self.hcell_centres_x
+                        x_centers = self.hcell_centres_x  # geolon
                         x_bounds = self.hcell_corners_x
-                        y_centers = self.hcell_centres_y
+                        y_centers = self.hcell_centres_y  # geolat
                         y_bounds = self.hcell_corners_y
                     case "U":
-                        x_centers = self.ucell_centres_x[:, i_start:]
+                        x_centers = self.ucell_centres_x[:, i_start:]  # geolon_u
                         x_bounds = self.ucell_corners_x[:, i_start:, :]
-                        y_centers = self.ucell_centres_y[:, i_start:]
+                        y_centers = self.ucell_centres_y[:, i_start:]  # geolat_u
                         y_bounds = self.ucell_corners_y[:, i_start:, :]
                     case "V":
-                        x_centers = self.vcell_centres_x[i_start:, :]
+                        x_centers = self.vcell_centres_x[i_start:, :]  # geolon_v
                         x_bounds = self.vcell_corners_x[i_start:, :, :]
-                        y_centers = self.vcell_centres_y[i_start:, :]
+                        y_centers = self.vcell_centres_y[i_start:, :]  # geolat_v
                         y_bounds = self.vcell_corners_y[i_start:, :, :]
                     case "C":
-                        x_centers = self.qcell_centres_x[i_start:, i_start:]
+                        x_centers = self.qcell_centres_x[i_start:, i_start:]  # geolon_c
                         x_bounds = self.qcell_corners_x[i_start:, i_start:, :]
-                        y_centers = self.qcell_centres_y[i_start:, i_start:]
+                        y_centers = self.qcell_centres_y[i_start:, i_start:]  # geolat_c
                         y_bounds = self.qcell_corners_y[i_start:, i_start:, :]
                     case _:
                         raise ValueError(