identify X and Y in rotated pole grids (#426)

* added grid mapping standard coordinate names

* update guess_coord test

Author: larsbuntemeyer

cf_xarray/criteria.py

@@ -94,14 +94,22 @@
         "positive": ("up", "down"),
     },
     "X": {
-        "standard_name": ("projection_x_coordinate",),
+        "standard_name": (
+            "projection_x_coordinate",
+            "grid_longitude",
+            "projection_x_angular_coordinate",
+        ),
         "_CoordinateAxisType": ("GeoX",),
         "axis": ("X",),
         "cartesian_axis": ("X",),
         "grads_dim": ("x",),
     },
     "Y": {
-        "standard_name": ("projection_y_coordinate",),
+        "standard_name": (
+            "projection_y_coordinate",
+            "grid_latitude",
+            "projection_y_angular_coordinate",
+        ),
         "_CoordinateAxisType": ("GeoY",),
         "axis": ("Y",),
         "cartesian_axis": ("Y",),
@@ -134,9 +142,9 @@
         "(z|nav_lev|gdep|lv_|[o]*lev|bottom_top|sigma|h(ei)?ght|altitude|depth|"
         "isobaric|pres|isotherm)[a-z_]*[0-9]*"
     ),
-    "Y": re.compile("y|j|nlat|nj"),
+    "Y": re.compile("y|j|nlat|rlat|nj"),
     "latitude": re.compile("y?(nav_lat|lat|gphi)[a-z0-9]*"),
-    "X": re.compile("x|i|nlon|ni"),
+    "X": re.compile("x|i|nlon|rlon|ni"),
     "longitude": re.compile("x?(nav_lon|lon|glam)[a-z0-9]*"),
 }
 regex["T"] = regex["time"]

cf_xarray/tests/test_accessor.py

@@ -1142,8 +1142,8 @@ def _check_attrs_equal(o, n):
         "nav_lev",
     ]
 )
-_X_NAMES = _make_names(["x", "nlon", "i", "ni"])
-_Y_NAMES = _make_names(["y", "nlat", "j", "nj"])
+_X_NAMES = _make_names(["x", "nlon", "i", "ni", "rlon"])
+_Y_NAMES = _make_names(["y", "nlat", "j", "nj", "rlat"])
 _Z_NAMES = _VERTICAL_NAMES + ["olevel", "level", "zlevel"]
 _LATITUDE_NAMES = _make_names(["lat", "latitude", "gphi", "nav_lat"])
 _LONGITUDE_NAMES = _make_names(["lon", "longitude", "glam", "nav_lon"])