MET Online Tutorial for METv3.0

Grid-Stat Tool: Configure

The behavior of Grid-Stat is controlled by the contents of the configuration file passed to it on the command line. The default Grid-Stat configuration file may be found in the METv3.0/data/config/GridStatConfig_default file. The configurations used by the test script may be found in the METv3.0/scripts/config/GridStatConfig* files. Prior to modifying the configuration file, users are advised to make a copy of the default:

    cp data/config/GridStatConfig_default tutorial/config/GridStatConfig_APCP_12
    cp data/config/GridStatConfig_default tutorial/config/GridStatConfig_POP_12

The configurable items for Grid-Stat are used to specify how the verification is to be performed. The Grid-Stat configuration file should look very similar to the one for Point-Stat. The configurable items include specifications for the following:

  • The forecast fields to be verified at the specified vertical level or accumulation interval.
  • The threshold values to be applied.
  • The areas over which to aggregate statistics - as predefined grids or configurable lat/lon polylines.
  • The confidence interval methods to be used.
  • The smoothing methods to be applied (as opposed to interpolation methods).
  • The types of verification methods to be used.

You may find a complete description of the configurable items in the MET Users Guide or in the comments of the configuration file itself. Please take some time to review them.

For this tutorial, we'll run Grid-Stat twice - once to verify the 12-hour accumulated precipitation output of PCP-Combine and once to apply the probabilistic verification methods to a 12-hour probability of precipitation forecast. In the first run, we'll use NetCDF for both the forecast and observation files. In the second run, we'll use a GRIB forecast file and a NetCDF observation file. While we'll use Grid-Stat to verify only one field at a time, it may be configured to verify more than one field at a time.

Open up the tutorial/config/GridStatConfig_APCP_12 file for editing with your preferred text editor and edit it as follows:

  • Set fcst_field[] = [ "APCP_12(*,*)" ];
    To verify the NetCDF variable of that name in the input file.
  • Set obs_field[] = [];
  • Set fcst_thresh[] = [ "gt0.0 ge5.0 ge10.0" ];
    To select 3 threshold values of interest.
  • Set obs_thresh[] = [];
  • Set mask_grid[] = [ "G212" ];
    To accumulate statistics over the NCEP Grid 212 region.
  • Set mask_poly[] = [ "MET_BASE/tutorial/out/gen_poly_mask/CONUS_G212_poly.nc",
    "MET_BASE/data/poly/EAST.poly",
    "MET_BASE/data/poly/WEST.poly" ];

    To accumulate statistics over the entire CONUS using the NetCDF output of the Gen-Poly-Mask tool and over the regions defined by the EAST and WEST polyline files.
  • Set nbr_width[] = [ 3, 5 ];
    To select two neighborhood sizes over which to accumulate neighborhood statistics.
  • Set cov_thresh[] = [ "ge0.5", "ge0.75" ];
    To define the fractional coverage threshold values of interest.
  • Set output_flag[] = [ 0, 2, 2, 0, 0, 2, 2, 0, 0, 0, 0, 0, 2, 2, 2, 1 ];
    To indicate that contingency table counts (CTC), contingency table statistics (CTS), continuous statistics (CNT), scalar partial sums (SL1L2), neighborhood contingency table counts (NBRCTC), neighborhood contingency table statistics (NBRCTS), neighborhood continuous statistics (NBRCNT), and the NetCDF difference field should be output.

arrow Note that we are not requesting multi-category contingency table output, MCTC and MCTS lines. While we are specifying multiple thresholds (gt0.0 ge5.0 ge10.0), they are not all of the same type ("gt" versus "ge") which would cause an error.

Save and close this file and open up the tutorial/config/GridStatConfig_POP_12 file for editing with your preferred text editor and edit it as follows:

  • Set fcst_field[] = [ "POP/Z0/PROB" ];
    To verify the 12-hour probability of precipitation forecast from the input GRIB file.
  • Set obs_field[] = [ "APCP_12(*,*)" ];
    To verify against the NetCDF variable of that name in the observation file.
  • Set fcst_thresh[] = [ "ge0.0 ge0.25 ge0.50 ge0.75 ge1.0" ];
    To define the threshold probabilities of interest.
  • Set obs_thresh[] = [ "gt0.0" ];
    So that any non-zero amount of precipitation verifies as correct.
  • Set mask_grid[] = [ "G212" ];
    To accumulate statistics over the NCEP Grid 212 region.
  • Set mask_poly[] = [ "MET_BASE/tutorial/out/gen_poly_mask/CONUS_G212_poly.nc",
    "MET_BASE/data/poly/EAST.poly",
    "MET_BASE/data/poly/WEST.poly" ];

    To accumulate statistics over the entire CONUS using the NetCDF output of the Gen-Poly-Mask tool and over the regions defined by the EAST and WEST polyline files.
  • Set output_flag[] = [ 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 2, 2, 0, 0, 0, 1 ];
    To indicate that probability contingency table counts (PCT), probability statistics (PSTD), joint/continuous probabilistic statistics (PJC), probabilistic ROC curve points (PRC), and the NetCDF difference field should be output.

Save and close this file.