def _mean_bias_reduction_quick(hind, bias, dim):
    """Quick reduction of mean bias over all initializations.

    Args:
        hind (xr.object): hindcast.
        bias (xr.object): bias.
        dim (str): Time dimension name in bias.

    Returns:
        xr.object: bias reduced hind

    """
    bias_reduced_hind = (
        hind.groupby(f"{dim}.dayofyear") - bias.groupby(f"{dim}.dayofyear").mean()
    )
    return bias_reduced_hind