Fix for pressure coordinate name variants plus enforce units to be hPa

src/CSET/operators/read.py

@@ -228,7 +228,7 @@ def callback(cube: iris.cube.Cube, field, filename: str):
         _lfric_time_coord_fix_callback(cube, field, filename)
         _longitude_fix_callback(cube, field, filename)
         _fix_spatial_coord_name_callback(cube)
-        _fix_pressure_coord_name_callback(cube)
+        _fix_pressure_coord_callback(cube)
 
     return callback
 
@@ -408,20 +408,26 @@ def _fix_spatial_coord_name_callback(cube: iris.cube.Cube):
         cube.coord(x_name).rename("grid_longitude")
 
 
-def _fix_pressure_coord_name_callback(cube: iris.cube.Cube):
-    """Rename pressure_level coordinate to pressure if it exists.
+def _fix_pressure_coord_callback(cube: iris.cube.Cube):
+    """Rename pressure coordinate to 'pressure' if it exists and ensure hPa units.
 
     This problem was raised because the AIFS model data from ECMWF
     defines the pressure coordinate with the name 'pressure_level' rather
-    than compliant CF coordinate names
+    than compliant CF coordinate names.
+
+    Additionally, set the units of pressure to be hPa.
     """
     # We only want to modify instances where the coordinate system is actually
     # latitude/longitude, and not touch the cube if the coordinate system is say
     # meters.
     for coord in cube.dim_coords:
-        if coord.name() == "pressure_level":
+        if coord.name() in ["pressure_level", "pressure_levels"]:
             coord.rename("pressure")
 
+    for coord in cube.dim_coords:
+        if coord.name() == "pressure":
+            cube.coord("pressure").convert_units("hPa")
+
 
 def _check_input_files(input_paths: list[str], filename_pattern: str) -> list[Path]:
     """Get an iterable of files to load, and check that they all exist.

tests/operators/test_read.py

@@ -245,17 +245,25 @@ def test_lfric_time_coord_fix_callback_no_time():
     assert len(cube.coords("time")) == 0
 
 
-def test_pressure_coord_fix_callback():
+def test_pressure_coord_name_fix_callback():
     """Check that pressure_level is renamed to pressure if it exists."""
     cube = iris.load_cube("tests/test_data/transect_test_umpl.nc")
     cube.coord("pressure").rename("pressure_level")
-    read._fix_pressure_coord_name_callback(cube)
+    read._fix_pressure_coord_callback(cube)
     assert (
         repr(cube.coords())
         == "[<DimCoord: time / (hours since 1970-01-01 00:00:00)  [...]  shape(2,)>, <DimCoord: pressure / (hPa)  [ 100., 150., ..., 950., 1000.]  shape(16,)>, <DimCoord: latitude / (degrees)  [-10.98, -10.94, ..., -10.82, -10.78]  shape(6,)>, <DimCoord: longitude / (degrees)  [19.02, 19.06, ..., 19.18, 19.22]  shape(6,)>, <DimCoord: forecast_reference_time / (hours since 1970-01-01 00:00:00)  [...]>, <AuxCoord: forecast_period / (hours)  [15., 18.]  shape(2,)>]"
     )
 
 
+def test_pressure_coord_unit_fix_callback():
+    """Check that pressure level units are hPa."""
+    cube = iris.load_cube("tests/test_data/transect_test_umpl.nc")
+    cube.coord("pressure").convert_units("Pa")
+    read._fix_pressure_coord_callback(cube)
+    assert repr(str(cube.coord("pressure").units)) == "'hPa'"
+
+
 def test_spatial_coord_rename_callback():
     """Check that spatial coord gets renamed if it is not grid_latitude."""
     # This cube contains 'latitude' and 'longitude'