def _get_default_var_dicts_planetos(dataset):
    """
    Returns dictionary mapping PlanetOS variable names to OpenOA variable names for a particular dataset

    Args:
        dataset (:obj:`string`): Dataset name ("merra2" or "era5")

    Returns:
        :obj:`dict`: Dictionary mapping reanalysis variable names from PlanetOS to standard OpenOA variable names
    """

    dataset = dataset.lower().strip()

    if dataset == "merra2":
        var_dict = {"U50M": "u_ms", "V50M": "v_ms", "T2M": "temperature_K", "PS": "surf_pres_Pa"}
    elif dataset == "era5":
        var_dict = {
            "eastward_wind_at_100_metres": "u_ms",
            "northward_wind_at_100_metres": "v_ms",
            "air_temperature_at_2_metres": "temperature_K",
            "surface_air_pressure": "surf_pres_Pa",
        }
    else:
        raise ValueError('Invalid dataset name. Currently, "merra2" and "era5" are supported.')

    return var_dict