mesh variable from_copernicusmarine

[reint-fischer]

Parcels version

v4-dev

Description

When loading in a fieldset using from_copernicusmarine, I wanted to check the grid.mesh that was being used. This is now available under the private name _mesh. I was surprised to find that it returns “flat”.

Code sample

# Load the CopernicusMarine data in the Agulhas region from the example_datasets
example_dataset_folder = parcels.download_example_dataset(
    "CopernicusMarine_data_for_Argo_tutorial"
)

ds_fields = xr.open_mfdataset(
    f"{example_dataset_folder}/*.nc", combine="by_coords"
).isel(depth=slice(0, 1))
ds_fields.load()  # load the dataset into memory

fieldset = parcels.FieldSet.from_copernicusmarine(ds_fields)

fieldset.U.grid._mesh

“flat"

[erikvansebille]

Thanks for catching this bug, @reint-fischer. It's because the default XGrid.mesh is "flat" at initialisation; we may want to reconsider that?

I'm surprised though, that other Kernels like the Argo kernel work; these would have assumed a spherical mesh?

In any case, I've fixed it (and added a unit test) in #2407