Computing fCoriG, e.g., for the EGshelfSJsec500m_3H_NONhydro dataset

[ThomasHaine]

Some SciServer datasets don't have the fCoriG variable, like EGshelfSJsec500m_3H_NONhydro. That's a pain because fCoriG is required to compute Ertel PV. fCoriG is the Coriolis parameter at cell corners.

Here's a code snippet that does the job:

    # Add fCoriG
    # Import packages:
    import numpy as _np
    import xarray as _xr
    
    # Extract parameters:
    paramsList = ["omega"]
    params2use = {par: od.parameters[par] for par in od.parameters if par in paramsList}
    omega = params2use["omega"]

    # Extract latitude and compute Coriolis parameter:
    fCoriG = 2.0*omega*_np.sin(_np.radians(od._ds["YG"]))

    # Metadata:
    fCoriG.attrs["units"] = "s^-1"
    fCoriG.attrs["long_name"] = "Coriolis parameter at corner points"
    fCoriG.attrs["OceanSpy_parameters"] = str(params2use)

    # Create ds
    ds = _xr.Dataset({"fCoriG": fCoriG}, attrs=od.dataset.attrs)

    # Merge into od:
    od = od.merge_into_oceandataset(ds)
    
    # Add Ertel PV:
    od = od.compute.Ertel_potential_vorticity()

Comments welcome!