MET Online Tutorial for METv3.0

MODE Tool: Output

As mentioned on the previous page, the output of MODE typically consists of 4 files: 2 ASCII statistics files, 1 NetCDF object file, and 1 PostScript summary plot. The output of any of these files may be disabled using the appropriate MODE command line argument. In this example, the output is written to the tutorial/out/mode directory as we requested on the command line.

The MODE output file naming convention is designed to contain the names of the forecast and observation fields and levels, the lead times, valid times, and accumulation times. If you rerun MODE on the same fields but with a slightly different configuration, the new output will override the old output, unless you redirect it to a different directory using the -outdir command line argument. The 4 MODE output files are described briefly below:

  • The PostScript file ends in .ps and was described on the previous page.
  • The NetCDF object file ends in _obj.nc and contains the raw and cluster object indices and boundary polylines for the simple objects.
  • The ASCII contingency table statistics file ends in _cts.txt.
  • The ASCII object statistics file ends in _obj.txt and contains all of the object and object comparison data.

Since we've already seen the PostScript summary plot, we'll skip that one here. Use the ncview utility (if available on your machine) to view the NetCDF object output of MODE:

    ncview tutorial/out/mode/mode_240000L_20050808_000000V_120000A_obj.nc&

Click through the variable names in the ncview window to see plots of the four object fields in the file. The fcst_obj_id and obs_obj_id contain the indices for the forecast and observation objects defined by MODE. The fcst_clus_id and obs_clus_id contain indices for the matched cluster objects. Now dump the header:

    ncdump -h tutorial/out/mode/mode_240000L_20050808_000000V_120000A_obj.nc

View the NetCDF header to see how the file is structured.

arrow The object colors plotted by ncview will generally not correspond to those in MODE's PostScript output.

Next, open up the tutorial/out/mode/mode_240000L_20050808_000000V_120000A_cts.txt contingency table statistics ASCII file using the text editor of your choice. This file is similar to the CTS output of Grid-Stat but much less complete. It contains 4 lines, a header row followed by contingency table statistics computed 3 ways:

  • The first row contains RAW in the FIELD column. The scores listed in this row are computed from the RAW forecast and observation fields. The raw fields are thresholded using the fcst_conv_thresh and obs_conv_thresh values specified to create 0/1 mask fields. Those mask fields are compared point by point to compute a contingency table. The scores listed in this row are derived from that contingency table.
  • The second row contains FILTER in the FIELD column. The scores listed in this row are computed from the filtered forecast and observation fields. The filtered fields are just what's left of the raw fields after the fcst_raw_thresh and obs_raw_thresh values have been applied. Those filtered fields are then thresholded using the fcst_conv_thresh and obs_conv_thresh values specified to create a 0/1 mask field. The mask fields are compared point by point, a contingency table is computed, and the corresponding statistics are listed in this row. Since no filtering was performed in this example, the contents of this FILTER row match the contents of the RAW row.
  • The third row contains OBJECT in the FIELD column. The scores listed in this row are computed from the forecast and observation OBJECT fields. In MODE, after objects have been defined, the field may be thought of as a 0/1 mask field, 1 at grid points contained inside an object and 0 everywhere else. The object mask fields are compared in this way point by point, a contingency table is computed, and the corresponding statistics are listed in this row.

This file is not meant to replicate or replace the functionality of the Grid-Stat tool which includes many more features and options. It is simply meant to provide a convenient way of seeing how the output of MODE compares to the traditional contingency table statistics that are often computed.

Close this file, and open up the tutorial/out/mode/mode_240000L_20050808_000000V_120000A_obj.txt object statistics ASCII file using the text editor of your choice. This file contains all of the object statistics in which most users will be interested. It contains 4 different line types which may be distinguished by the contents of the OBJECT_ID column:

  • The rows containing FNNN and ONNN in that column give information about the simple forecast and observation objects, respectively. NNN refers to the simple object number.
  • The rows containing FNNN_ONNN in that column give information about pairs of simple objects.
  • The rows containing CFNNN and CONNN in that column give information about the cluster forecast and observation objects, respectively. NNN refers to the cluster object number.
  • The rows containing CFNNN_CONNN in that column give information about pairs of cluster objects.

arrow In the ASCII MODE statistics file, the value of 000 for NNN in the OBJECT_ID column indicates that that object was not matched.

Each line in this file contains the same number of columns. However, only certain columns are applicable to certain line types. For example, the CENTROID_X and CENTROID_Y columns contain valid data for simple object lines, but not for pairs of simple object lines. The opposite is true for the CENTROID_DIST column which gives the distance between the centroids of two objects. Columns which are not applicable to a given line type are filled with a value of NA.

Please refer to the MET Users Guide for a more thorough description of the MODE output. At this point, feel free to return to the previous page and play around with the MODE configuration settings.