docs: def persist(filename):
      """
      Append the linke turbidity projected (using lat lon) as variables of
      the netcdf file.
  
      Keyword arguments:
      filename -- the name of a netcdf file.
      """
      linkes_projected = obtain_to(filename, compressed=False)
      keys = sorted(linkes_projected.keys())
      values = np.vstack([map(lambda k: linkes_projected[k], keys)])
      with nc.loader(filename) as root:
          data = nc.getvar(root, 'data')
          linke = nc.getvar(root, 'linke', 'f4', source=data)
          linke[:] = values