data_unibremen/coordinates.py at main · mackenziejewell/data_unibremen · GitHub

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# Description: Functions to generate url path to coordinate files for Uni Bremen data

from pyhdf.SD  import *
from metpy.units import units
import xarray as xr

def name_area_file(res: str, hem: str, include_url: bool = True):

    """Generate the name of the cell area file for a given resolution and hemisphere.
    INPUT:
    - res: str, resolution of desired file ('3125, '6250', '12500', '25000', '1000ma2')
    - hem: str, hemisphere of desired file ('n', 's')
    - include_url: whether to include remote url in filename (True) or file name only (False)
    OUTPUT:
    - file: str, url path to coordinate file

    Latest recorded update:
    02-13-2025
    """

    area_path = 'https://data.seaice.uni-bremen.de/grid_coordinates/GridCellArea/'

    # convert to km
    resstr = str(float(res)*units('m').to('km').magnitude)

    filename = f'PolStereo_GridCellArea_{hem}{resstr}km_Arctic.nc'

    if include_url:
        file = area_path + filename
    else:
        file = filename

    return file


def name_coordinate_file(res: str, hem: str, include_url: bool = True):

    """Generate the name of the coordinate file for a given resolution and hemisphere.
    INPUT:
    - res: str, resolution of desired file ('3125, '6250', '12500', '25000', '1000ma2')
    - hem: str, hemisphere of desired file ('n', 's')
    - include_url: whether to include remote url in filename (True) or file name only (False)
    OUTPUT:
    - file: str, url path to coordinate file
    Latest recorded update:
    02-13-2025
    """

    coordinates_path = 'https://data.seaice.uni-bremen.de/grid_coordinates/'

    group = hem+res

    if hem == 'n':
        region = 'Arctic'
    elif hem == 's':
        region = 'Antarctic'

    # cell coordinate (lat/lon) file
    filepath = coordinates_path + f'{group}/'

    if res == '1000ma2':
        # wouldn't work if interested in SH files but I don't know if these exist
        # if they do, address later! Website down right now
        coord_file = f'coordinates_npstere_1km_arctic.nc'
    elif res == '3125':
        coord_file = f'LongitudeLatitudeGrid-{group}-{region}3125.hdf'
    elif res == '25000':
        coord_file = f'PolStereo_LonLat-{hem}25km-{region}.hdf'
    else:
        coord_file = f'LongitudeLatitudeGrid-{group}-{region}.hdf'

    if include_url:
        file = filepath + coord_file
    else:
        file = coord_file

    return file


def open_coord_file(file):
    """Open coordinate file from locally downlaoded file.
    Latest recorded update:
    02-13-2025
    """


    if file.split('.')[-1] == 'nc':
        # open file
        try:
            ds = xr.open_dataset(file)
            ds.close()
        # raise an error if file can't be opened
        except Exception as e:
            print(f"{e}, error opening {file}")
        lon = ds.lon.values
        lat = ds.lat.values


    else:
        # open file
        try:
            f = SD(file, mode=1)
        # raise an error if file can't be opened
        except Exception as e:
            print(f"{e}, error opening {file}")
        lon = f.select('Longitudes')[:]
        lat = f.select('Latitudes')[:]

    return lon, lat