def correct_units(radar):
    """
    Correct units according to CF/convention.

    Parameter:
    ==========
    radar: Radar object
        Py-ART data structure.
    """
    ufields = {"cross_correlation_ratio": "1", "spectrum_width": "m s-1"}

    for k, v in ufields.items():
        try:
            radar.fields[k]["units"] = v
        except KeyError:
            pass

    radar.sweep_mode["units"] = " "
    radar.scan_rate["units"] = "degree s-1"
    radar.instrument_parameters["nyquist_velocity"]["units"] = "m s-1"

    return None