Append the linke turbidity projected (using lat lon) as variables of
    the netcdf file.

    Keyword arguments:
    filename -- the name of a netcdf file.

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