def build_param_dict(stnm, year, month, day_hour):
    """
    Builds a dictionary containing the station number, year, month, and day/hour for the desired atmospheric sounding data.
    
    Parameters
    ----------
    stnm : string
        String of the station identifier, e.g. '70261' for PAFA, Fairbanks Int'l Airport.
    year : string
        String of the year, e.g. '2021'.
    month : string
        String of the month, e.g. '01'.
    day_hour : string
        String of the combined day and hour, e.g. '0100' for the first day of the month as '01', and for the beginning of the day in UTC as '00'.

    Returns
    -------
    param_dict : dict
        A dictionary containing the station number, year, month, and day/hour of the desired date and location.
    """
    
    param_dict = {'STNM': stnm, 'YEAR': year, 'MONTH': month, 'FROM': day_hour, 'TO': day_hour}

    return param_dict