How to take the time average using time bounds?

[briochemc]

👋 Noob here so maybe this is a dumb question but here I go.

Given a dataset ds with some variable foo with a time coordinate (among others like x, y, z, and so on) that also includes time_bnds, what's the preferred way to get the time-weighted average of foo (that uses the time_bnds data)?

Adapting Calculating Seasonal Averages from Time Series of Monthly Means from the docs, I know I could manually extract deltatime = ds["time_bnds"].sel(bnds=1) - ds["time_bnds"].sel(bnds=0) and build weights from weights = deltatime / deltatime.sum() and then do the weighted sum (foo * weights).sum() or something similar, but I was hoping there is a predefined automatic way to that in a single liner with xarray. Is that the case?

[arfriedman]

Hi @briochemc check out xCDAT, which builds on xarray.
In particular: https://xcdat.readthedocs.io/en/stable/examples/temporal-average.html

[arfriedman]

hi @briochemc here's information on the xCDAT temporal accessor, which uses time bounds: https://xcdat.readthedocs.io/en/stable/generated/xcdat.temporal.TemporalAccessor.html
Note that the functionality is still evolving: xCDAT/xcdat#412

[tomvothecoder]

Thanks @arfriedman for plugging xCDAT! Yes the temporal accessor uses time bounds.

@briochemc, we'll update the docs to make this info clear. Let us know if you have any questions over at https://github.com/xCDAT/xcdat/discussions!

[tomvothecoder]

Below are the sections of code in xCDAT where time bounds are used to generate weights and where weights are applied to the variable:

• _averager(): https://github.com/xCDAT/xcdat/blob/e6dbed5c7037a0ad09a90bb364f7aee3a25915e3/xcdat/temporal.py#L701-L708
• _average(): https://github.com/xCDAT/xcdat/blob/e6dbed5c7037a0ad09a90bb364f7aee3a25915e3/xcdat/temporal.py#L1015-L1018
• _group_average(): https://github.com/xCDAT/xcdat/blob/e6dbed5c7037a0ad09a90bb364f7aee3a25915e3/xcdat/temporal.py#L1049-L1067
• _get_weights() : https://github.com/xCDAT/xcdat/blob/e6dbed5c7037a0ad09a90bb364f7aee3a25915e3/xcdat/temporal.py#L1090-L1148

[briochemc]

BTW, I just realized... Should you not add xcdat to the ecosystem list?

[tomvothecoder]

@briochemc It was recently added to the main branch and will be included in the next release.
"Latest" version of docs: https://docs.xarray.dev/en/latest/ecosystem.html#geosciences