The behavior of PB2NC is controlled by the contents of the configuration file passed to it on the command line. The default PB2NC configuration may be found in the met-8.0/share/met/config/PB2NCConfig_default file. Additional information about configuration files can be found in $MET_BASE/config/README file. The configuration used by the test script may be found in the met-8.0/scripts/config/PB2NCConfig_G212 file. Prior to modifying the configuration file, users are advised to make a copy of the default:

Open up the $MET_TUTORIAL_DATA/config/PB2NCConfig_tutorial file for editing with your preferred text editor.

The configurable items for PB2NC are used to filter out the PrepBufr observations that should be retained or derived. You may find a complete description of the configurable items in the MET Users Guide or in the $MET_BASE/config/README file. Please take some time to review them.

For this tutorial, edit the $MET_TUTORIAL_DATA/config/PB2NCConfig_tutorial file as follows:

• Set message_type = [ "ADPUPA", "ADPSFC" ]; to retain only those 2 message types.
• In obs_window, set beg = -1800; and end = 1800; so that only observations within 30 minutes (1800 seconds) of the reference time will be retained.
• In mask, set grid = "G212"; to retain only those observations residing within the bounds of NCEP Grid 212 (on which the forecast data resides).
• Set obs_bufr_var = [ "QOB", "TOB", "ZOB", "UOB", "VOB", "D_WIND", "D_RH" ]; to retain observations for specific humidity, temperature, the u-component of wind, and the v-component of wind and to derive observation values for wind speed and relative humidity. This configuration replaces obs_grib_code. A list of valid GRIB codes, their units, and the corresponding abbreviations may be found here.

Save and close this file.

Next, run PB2NC on the command line using the following command:

PB2NC is now filtering the observations from the input PrepBufr file using the configuration settings we specified and writing the output to the NetCDF file name we chose. This should take a few minutes to run. As it runs, you should see several status messages printed to the screen to indicate progress. You may use the -v command line option to turn off or change the amount of log information printed to the screen.

Runtime Errors

Listed below are two common error messages from the BUFRLIB:

1. +++++++++++++++++++++++WARNING+++++++++++++++++++++++++
   BUFRLIB: OPENBF - INPUT BUFR FILE IN UNIT 11 IS EMPTY
   +++++++++++++++++++++++WARNING+++++++++++++++++++++++++

   For this error message, ensure that BUFRLIB was built with the *same* family of compilers used to build MET.

2. **************BUFR ARCHIVE LIBRARY ABORT*****************
   BUFRLIB: OPENBF - FIRST 4 BYTES READ FROM RECORD IN INPUT FILE
   CONNECTED TO UNIT 11 NOT 'BUFR', DOES NOT CONTAIN BUFR DATA
   **************BUFR ARCHIVE LIBRARY ABORT*****************
3. For this error message, refer to the PB2NC Tool: General page and follow the instructions regarding the --disable-block4 configure option.

When PB2NC is finished, you'll see a summary of how many PrepBufr messages were processed, retained, and rejected for various reasons. In that output, we see that 69833 PrepBufr messages were processed of which only 8415 were retained. And from those 8415 messages, 62443 observation values were extracted.

You may view the output NetCDF file that PB2NC wrote using the ncdump utility (if available on your machine). Run the following command to view the header of the NetCDF output file:

In the NetCDF header, we see that the file contains 22 variables. The obs_ variables contain information about the observations while the hdr_ arrays contain information about the observing location, type, and time. See the comments in the ncdump output for more details.

When processing Global GDAS PrepBufr observations, users should note that the quality marker is set to a value of 9 for surface observations. This is done to prevent them from being used in the data assimilation process. However, these observations will not be retained by the default PB2NC configuration. Users may configure PB2NC with quality_mark_thesh = 9; to retain GDAS surface observations.