We now shift to a discussion of the MET PCP-Combine tool and will practice running it directly on the command line. Later in this session, we will run PCP-Combine as part of a METplus use case.
The PCP-Combine tool is used (if needed) to add, subtract, or sum accumulated precipitation from several gridded data files into a single NetCDF file containing the desired accumulation period. Its NetCDF output may be used as input to the MET statistics tools. PCP-Combine may be configured to combine any gridded data field you'd like. However, all gridded data files being combined must have already been placed on a common grid. The copygb utility is recommended for re-gridding GRIB files. In addition, the PCP-Combine tool will only sum model files with the same initialization time unless it is configured to ignore the initialization time.
View the usage statement for PCP-Combine by simply typing the following:
|[[-sum] sum_args] | [-add input_files] | [-subtract input_files] | [-derive stat_list input_files]
(Note: "|" means "or")
|[-sum] sum_args||Precipitation from multiple files containing the same accumulation interval should be summed up using the arguments provided.|
|-add input_files||Data from one or more files should be added together where the accumulation interval is specified separately for each input file.|
|-subtract input_files||Data from exactly two files should be subtracted.|
|-derive stat_list input_files||The comma-separated list of statistics in "stat_list" (sum, min, max, range, mean, stdev, vld_count) should be derived using data from one or more files.|
|out_file||Output NetCDF file to be written.|
|[-field string]||Overrides the default use of accumulated precipitation (optional).|
|[-name list]||Overrides the default NetCDF variable name(s) to be written (optional).|
|[-log file]||Outputs log messages to the specified file|
|[-v level]||Level of logging|
|[-compress level]||NetCDF file compression|
Use the -sum, -add, -subtract, or -derive command line option to indicate the operation to be performed. Each operation has its own set of required arguments.