def extract_source_region(region):
    """
    DESCRIPTION:
    ============
        Give the lon/lat of the rectangle defining each source

    ARGUMENTS:
    ==========
        region, currently defined regions are: taklamakan, north_west, mongolia, jungger_basin
                and quaidam_basin

    RETURN:
    ======
        lon0,lon1,lat0,lat1

    """

    if region == 'taklamakan':
        return 75, 90, 36 ,42
    elif region == 'north_west':
        return 100, 110, 37, 42
    elif region == 'mongolia':
        return 95, 110, 43, 50
    elif region == 'jungger_basin':
        return 80, 90, 43, 47
    elif region == 'quaidam_basin':
        return 90, 100, 35, 40
    else:
        raise(ValueError(f'{region} is not defined'))