Make it possible to regrid to the standard CORDEX domains

[bouweandela]

For working with CORDEX data, it would be useful if the standard CORDEX domains could be specified as a target grid for the esmvalcore.preprocessor.regrid function. I propose to add this as a feature.

[bouweandela]

@ghossh will look into this. The idea would be to update the function

ESMValCore/esmvalcore/preprocessor/_regrid.py

Line 596 in 51b2dcd

def _get_target_grid_cube(

such that if the target_grid argument is a string that matches one of the CORDEX regions, e.g. EUR-11, a cube with that grid will be returned. Example code for constructing such a grid is available here:
https://py-cordex.readthedocs.io/en/latest/index.html#features
and somewhat similar code lives here:

ESMValCore/esmvalcore/cmor/_fixes/cordex/cordex_fixes.py

Lines 146 to 192 in 51b2dcd

	def _fix_rotated_coords(self, cube, domain, domain_info):
	"""Fix rotated coordinates."""
	for dim_coord in ["rlat", "rlon"]:
	old_coord = cube.coord(domain[dim_coord].standard_name)
	old_coord_dims = old_coord.cube_dims(cube)
	points = domain[dim_coord].data
	coord_system = iris.coord_systems.RotatedGeogCS(
	grid_north_pole_latitude=domain_info["pollat"],
	grid_north_pole_longitude=domain_info["pollon"],
	)
	new_coord = iris.coords.DimCoord(
	points,
	var_name=dim_coord,
	standard_name=domain[dim_coord].standard_name,
	long_name=domain[dim_coord].long_name,
	units=Unit("degrees"),
	coord_system=coord_system,
	)
	self._check_grid_differences(old_coord, new_coord)
	new_coord.guess_bounds()
	cube.remove_coord(old_coord)
	cube.add_dim_coord(new_coord, old_coord_dims)
	def _fix_geographical_coords(self, cube, domain):
	"""Fix geographical coordinates."""
	for aux_coord in ["lat", "lon"]:
	old_coord = cube.coord(domain[aux_coord].standard_name)
	cube.remove_coord(old_coord)
	points = domain[aux_coord].data
	bounds = domain[f"{aux_coord}_vertices"].data
	new_coord = iris.coords.AuxCoord(
	points,
	var_name=aux_coord,
	standard_name=domain[aux_coord].standard_name,
	long_name=domain[aux_coord].long_name,
	units=Unit(domain[aux_coord].units),
	bounds=bounds,
	)
	if aux_coord == "lon" and new_coord.points.min() < 0.0:
	lon_inds = (new_coord.points < 0.0) & (old_coord.points > 0.0)
	old_coord.points[lon_inds] = old_coord.points[lon_inds] - 360.0
	self._check_grid_differences(old_coord, new_coord)
	aux_coord_dims = cube.coord(var_name="rlat").cube_dims(
	cube,
	) + cube.coord(var_name="rlon").cube_dims(cube)
	cube.add_aux_coord(new_coord, aux_coord_dims)