def METHOD_NAME():
    """
    Load fieldijn from npz file created with NCEP_test.py
    helper function, compute ensemble mean and spread, compute
    difficulty index for a set of thresholds, plot and save the results.
    """
    filename = os.environ.get('DIFF_INDEX_INPUT_FILENAME')
    lats, lons, fieldijn = load_data(filename)
    # Convert m/s to knots
    units = os.environ.get('DIFF_INDEX_UNITS')
    mps2kn = 1.94384
    fieldijn = mps2kn * fieldijn
    # Ensemble mean, std dev
    muij, sigmaij = compute_stats(fieldijn)
    # Windspeed envelope
    Aplin = compute_wind_envelope()
    # Difficulty index for a set of thresholds
    #thresholds = np.arange(os.environ.get('DIFF_INDEX_THRESH_START'), os.environ.get('DIFF_INDEX_THRESH_END'), os.environ.get('DIFF_INDEX_THRESH_STEP'))
    start = float(os.environ.get('DIFF_INDEX_THRESH_START'))
    stop = float(os.environ.get('DIFF_INDEX_THRESH_END'))
    step = float(os.environ.get('DIFF_INDEX_THRESH_STEP'))
    thresholds = np.arange(start, stop, step)
    dij = compute_difficulty_index(fieldijn, muij, sigmaij, thresholds, Aplin=Aplin)
    # Plot and save difficulty index figures
    figs = plot_difficulty_index(dij, lats, lons, thresholds, units)
    save_start = float(os.environ.get('DIFF_INDEX_SAVE_THRESH_START'))
    save_stop = float(os.environ.get('DIFF_INDEX_SAVE_THRESH_STOP'))
    save_step = float(os.environ.get('DIFF_INDEX_SAVE_THRESH_STEP'))
    save_thresh = np.arange(save_start, save_stop, save_step)
    save_difficulty_figures(figs, save_thresh, units)
    # Plot and save ensemble mean, std_dev
    mu_fig, sigma_fig =\
        plot_statistics(muij, sigmaij, lats, lons, units=units)
    save_stats_figures(mu_fig, sigma_fig)