def calc_time_series(dataset):
    """ Calculate time series mean values for a dataset

    :param dataset: Dataset object
    :type dataset: :class:`dataset.Dataset`

    :returns: time series for the dataset of shape (nT)
    """
    t_series = []
    for t in range(dataset.values.shape[0]):
        t_series.append(dataset.values[(t), :, :].mean())
    return t_series
