METplus Practical Session Guide (Version 4.0) | MET Tool: PB2NC > Output

PB2NC Tool: Output

When PB2NC is finished, you may view the output NetCDF file it wrote using the ncdump utility.

Run the following command to view the header of the NetCDF output file:
ncdump -h tutorial_pb_run1.nc

In the NetCDF header, you'll see that the file contains nine dimensions and nine variables. The obs_arr variable contains the actual observation values. The obs_qty variable contains the corresponding quality flags. The four header variables (hdr_typ, hdr_sid, hdr_vld, hdr_arr) contain information about the observing locations.

The obs_varobs_unit, and obs_desc variables describe the observation variables contained in the output. The second entry of the obs_arr variable (i.e. var_id) lists the index into these array for each observation. For example, for observations of temperature, you'd see TMP in obs_varKELVIN in obs_unit, and TEMPERATURE OBSERVATION in obs_desc. For observations of temperature in obs_arr, the second entry (var_id) would list the index of that temperature information.

Inspect the output of ncdump before continuing.

Plot-Point-Obs

The plot_point_obs tool plots the location of these NetCDF point observations. Just like plot_data_plane is useful to visualize gridded data, run plot_point_obs to make sure you have point observations where you expect.

Run the following command:
plot_point_obs \
tutorial_pb_run1.nc \
tutorial_pb_run1.ps
Display the output PostScript file by running the following command:
gv tutorial_pb_run1.ps &

Each red dot in the plot represents the location of at least one observation value. The plot_point_obs tool has additional command line options for filtering which observations get plotted and the area to be plotted.

View its usage statement by running the following command:
plot_point_obs

By default, the points are plotted on the full globe.

Next, try rerunning plot_point_obs using the -data_file option to specify the grid over which the points should be plotted:
plot_point_obs \
tutorial_pb_run1.nc \
tutorial_pb_run1_zoom.ps \
-data_file ${METPLUS_DATA}/met_test/data/sample_fcst/2007033000/nam.t00z.awip1236.tm00.20070330.grb

MET extracts the grid information from the first record of that GRIB file and plots the points on that domain.

Display the output PostScript file by running the following command:
gv tutorial_pb_run1_zoom.ps &

The plot_data_plane tool can be run on the NetCDF output of any of the MET point observation pre-processing tools (pb2ncascii2ncmadis2nc, and lidar2nc).