def select_region(ds, region=None):
    """
    Select region based on latitude or other.
    
    Args:
        ds: xarray dataset.
        region (str): string representation of region. defaults to None.
        
    Returns:
        subset array based on selected region.
        
    """
    dict_region = {'NH':     (30, 90),
                   'TP':     (-29, 29),
                   'SH':     (-60, -30),
                   'NOANT':  (-60, 90),
                   'FIRST':  (61, 90),
                   'SECOND': (31, 60),
                   'THIRD':  (1, 30),
                   'FOURTH': (-29, 0),
                   'FIFTH':  (-60, -30),
                  }
    
    if region:
        
        return ds.sel(lat=slice(dict_region[region][0], dict_region[region][1]))
    
    if not region:
        
        return ds