HindcastEnsemble.remove_bias() experimental for NWP leads

Describe the bug

• cross_validate=True doesnt work at all, if non-annual leads
• unsure about the behaviour in general for non-annual leads
• likely some completely different approach to bias reduction like smoothing needs to be implemented

became apparent in #603

Code Sample

requires #603 #529

with climpred.set_options(seasonality="dayofyear"):
        dayofyear_seasonality = hindcast.remove_bias(
            alignment=alignment, cross_validate=cross_validate
        )
with climpred.set_options(seasonality="weekofyear"):
        weekofyear_seasonality = hindcast.remove_bias(
            alignment=alignment, cross_validate=cross_validate
        )
assert not weekofyear_seasonality.get_initialized().identical(
        dayofyear_seasonality.get_initialized()

Expected behavior

• reduce bias with bias only from seasonality, e.g. initialized.init.dt.dayofyear or initialized.init.dt.month
• enable cross_validate=True: dont bias reduce initialization with that years bias

How to approach

1. Write down how bias reduction is supposed to work
2. Implement code

Easier to implement once #575 is merged: bias is calculated in time but named init

[judithberner]

Here is some code based on Riley’s and updated by Abby. My feeling is it’s not the latest version … https://github.com/judithberner/climpred_CESM1_S2S/blob/main/0.03_generate_member_anomalies_S2S.ipynb @abjaye

[aaronspring]

Closed by #645