def flip_cold(ds):
    """Flip mhw intensities if cold spell.

    Parameters
    ----------
    ds: xarray Dataset
        Includes MHW properties

    Returns
    -------
    ds: xarray Dataset
        Includes MHW properties with flipped values for intensities
    """

    for varname in ds.keys():
        if 'intensity' in varname and '_var' not in varname:
            ds[varname] = -1*ds[varname]
    return ds