Bugfix on hybrid sigma-pressure to constant pressure level interpolation

[yingkaisha]

Bugfix

• Minor fixes on credit.interp. Now it allows user-defined model-level coefficient names.
• Added some documentation to the script.
• Now geopotential at surface is loaded from model_level_file instead of the rollout files. This variable is static and typically not an output.
• A new file test_interp_static.nc is added to pair to the existing test_interp.nc.

[yingkaisha]

Ready

[djgagne]

I am ok with everything but adding the surface geopotential height to the model level netcdf file. I currently include the model level file in the credit metadata since it's a very small file, and adding surface geopotential would make the file a lot bigger. The ERA5 model levels and their coefficients are also constant across different spatial resolutions, whereas the surface geopotential field is not. When I call the pressure interpolation in credit/output.py, I link the surface geopotential variable to the model state xarray Dataset.

miles-credit/credit/output.py

Lines 178 to 192 in b27e22f

	if "interp_pressure" in conf["predict"].keys():
	if "surface_geopotential_var" in conf["predict"]["interp_pressure"].keys():
	surface_geopotential_var = conf["predict"]["interp_pressure"][
	"surface_geopotential_var"
	]
	else:
	surface_geopotential_var = "Z_GDS4_SFC"
	with xr.open_dataset(conf["data"]["save_loc_static"]) as static_ds:
	ds_merged[surface_geopotential_var] = static_ds[
	surface_geopotential_var
	]
	pressure_interp = full_state_pressure_interpolation(
	ds_merged, **conf["predict"]["interp_pressure"]
	)
	ds_merged = xr.merge([ds_merged, pressure_interp])

[yingkaisha]

surface geopotential

surface geopotential is constant.
surface geopotential ≠ surface pressure