Add remove scalar coordinates operator

src/CSET/operators/misc.py

@@ -81,6 +81,25 @@ def remove_attribute(
     return cubes
 
 
+def remove_scalar_coords(cubes, coords):
+    """Remove scalar coordinates.
+
+    examples would be: realization, forecast_reference_time from model cubes.
+    """
+    if not isinstance(cubes, CubeList):
+        cubes = CubeList([cubes])
+
+    for cube in cubes:
+        for coord_name in coords:
+            if cube.coords(coord_name):
+                coord = cube.coord(coord_name)
+                # only remove if scalar
+                if cube.coord_dims(coord) == ():
+                    cube.remove_coord(coord)
+
+    return cubes
+
+
 def addition(addend_1, addend_2):
     """Addition of two fields.
 

tests/operators/test_misc.py

@@ -541,3 +541,41 @@ def test_extract_common_points_nocommonpoints(vertical_profile_cube):
         misc.extract_common_points(
             cubes=iris.cube.CubeList([cube1, cube2]), coordinate="pressure"
         )
+
+
+def test_remove_scalar_coord():
+    """Test that scalar coordinate be removed."""
+    # Create simple 1D cube
+    data = np.arange(5)
+    time = iris.coords.DimCoord(
+        np.arange(5), standard_name="time", units="hours since 1970-01-01"
+    )
+    cube = iris.cube.Cube(data, dim_coords_and_dims=[(time, 0)])
+    # Add a scalar coord
+    realization = iris.coords.AuxCoord(1, long_name="realization")
+    cube.add_aux_coord(realization)
+    # Check it's present and scalar
+    assert cube.coords("realization")
+    assert cube.coord_dims("realization") == ()
+    # Run function
+    out = misc.remove_scalar_coords(cube, ["realization"])
+    # Check it’s removed
+    cube_out = out[0]
+    assert not cube_out.coords("realization")
+
+
+def test_not_remove_non_scalar_coord():
+    """Test that non-scalar coordinate is not removed."""
+    # Create 1D cube
+    data = np.arange(5)
+    time = iris.coords.DimCoord(
+        np.arange(5), standard_name="time", units="hours since 1970-01-01"
+    )
+    cube = iris.cube.Cube(data, dim_coords_and_dims=[(time, 0)])
+    # Confirm it's non-scalar
+    assert cube.coord_dims("time") != ()
+    # Run function
+    out = misc.remove_scalar_coords(cube, ["time"])
+    # Check it is still present
+    cube_out = out[0]
+    assert cube_out.coords("time")