issues: 1172229856

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id node_id number title user state locked assignee milestone comments created_at updated_at closed_at author_association active_lock_reason draft pull_request body reactions performed_via_github_app state_reason repo type
1172229856 I_kwDOAMm_X85F3s7g 6374 Should the zarr backend support NCZarr conventions? 22245117 closed 0     18 2022-03-17T11:00:17Z 2022-04-14T15:36:05Z 2022-04-14T15:36:05Z CONTRIBUTOR      

What is your issue?

As part of the CZI EOSS4 grant, at B-Open we are keen on improving xarray/zarr cross-community conventions. It looks like xarray's "zarr" backend does not support Unidata NCZarr conventions while NetCDF-c>=4.8.1 supports xarray conventions.

Currently, it is possible to open a NCZarr data source using the "netcdf4" backend only. Here is an example: ```python import xarray as xr import numpy as np

ds = xr.Dataset( { "a": (("y", "x"), np.random.rand(6).reshape(2, 3)), "b": (("y", "x"), np.random.rand(6).reshape(2, 3)), }, coords={"y": [0, 1], "x": [10, 20, 30]}, ) ds.to_netcdf("file://test.nczarr#mode=nczarr")

ds_from_nczarr = xr.open_dataset("file://test.nczarr#mode=nczarr", engine="netcdf4") xr.testing.assert_identical(ds, ds_from_nczarr)

xr.open_dataset("test.nczarr", engine="zarr")

KeyError: 'Zarr object is missing the attribute _ARRAY_DIMENSIONS, which is required for xarray to determine variable dimensions.'

```

Would the community benefit from a "zarr" backend compatible with NCZarr as well? @rsignell-usgs and @rabernat suggested to discuss this within the xarray community, but I don't think a dedicated issue has been opened yet.

cc: @alexamici @aurghs @joshmoore

 
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   completed 13221727 issue

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