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@rpnaut see the discussion in https://github.com/xarray-contrib/cf-xarray/issues/10 . That discussion focuses more on using the bounds to properly weight points when resampling.

But we could also make .cf.resample generate time bounds and set appropriate attributes on the returned object.

Maybe, I will look to create a wrapper to handle the time_bounds issue for files following the cf-conventions. Note, that not only resample operations should modify the time_bounds, but also the reselect process should take care about time_bounds. As an example, we assume to have in one file A instantenous data (two times a day at 00 UTC and 12 UTC) and in the other file B aggregated data (daily averages with time stamps defined at the end of the aggregation interval). The reselection process of A in B should pick up only the times 12 UTC from file A (or even better: no time steps because aggregation interval in file B is not compatible with instantenous values).

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Sorry, xarray doesn’t handle time bounds directly, nor does it update metadata according to cfconventions. These were intentional design choices to keep xarray simple, but in principle you could layer cf convention handling on top of xarray.

Nor does it bring along bounds variables when extracting variables from a dataset, e.g. double time(time) ; time:long_name = "time" ; time:cartesian_axis = "T" ; time:calendar_type = "NOLEAP" ; time:bounds = "time_bounds" ; time:units = "days since 0001-01-01" ; time:calendar = "NOLEAP" ; When a variable using the time dimension is extracted from a Dataset, the time_bounds variable is missing.

Is this also an intentional choice or something that xarray could/should support? Or does already and I've missed how to invoke this.

Edit: I've just realised, how is xarray supposed to "bring along" another variable in a DataArray object? I'll leave this query as maybe there is a solution? Have a bounds attribute similar to the coords attribute?

Is this just a dupe of https://github.com/pydata/xarray/issues/1475 ?

One thing I’ll note is that you probably want to make the time bounds variables coordinates rather than data variables. But that means the time bounds will probably simply be dropped when you resample.

Sorry, xarray doesn’t handle time bounds directly, nor does it update metadata according to cfconventions. These were intentional design choices to keep xarray simple, but in principle you could layer cf convention handling on top of xarray.

For this sort of analysis, using a tool like Iris designed to follow cf conventions might make sense. You can convert directly between iris cubes and xarray DataArray objects.

I want to add that sometimes the variable time_bnds is already gone after resampling.