METplus Practical Session Guide (Version 4.0) | Session 1: METplus Setup/Grid-to-Grid > MET Tool: PCP-Combine

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.

PCP-Combine Functionality

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.

PCP-Combine Usage

View the usage statement for PCP-Combine by simply typing the following:

Usage: pcp_combine  
  [[-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.