Support overlapping/rolling windows for climatology calculations

[andreas-grafberger]

Is your feature request related to a problem? Please describe.

For some of our hydrology use cases, we compute smooth daily climatologies with a sliding window where each day-of-year pools data from surrounding days across all years. For example, a 31-day window centered on each target day, where consecutive windows overlap by 30 days. This produces stable, smoothly varying statistics across the year.

Currently, earthkit.transforms.climatology.quantiles (which we'd like to use, but the same would apply to other functions in earthkit.transforms.climatology) exposes a bin_width parameter that produces non-overlapping bins.

Would it be possible to add a rolling window mode to the climatology module? For example, by adding a window (and stride?) parameter? I'm also happy to follow up with a few API proposals.

FYI; The legacy script we're trying to replace lives here: https://github.com/ecmwf/hyve/blob/main/src/hyve/tools/clim_benchmark.py

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[colonesej]

FYI: https://flox.readthedocs.io/en/latest/user-stories/overlaps.html

[chpolste]

We're also interested in this at earthkit-climate as we are moving to earthkit-transforms for aggregations. At the moment we're using https://xclim.readthedocs.io/en/stable/apidoc/xclim.core.html#xclim.core.calendar.percentile_doy.

@AntonioCC808 fyi