METplus Practical Session Guide (Version 5.0) | Session 1: Grid-to-Grid > MET Tool: PCP-Combine

IMPORTANT NOTE: If you are returning to the tutorial, you must source the tutorial setup script before running the following instructions. If you are unsure if you have done this step, please navigate to the Verify Environment is Set Correctly page.

We now shift to a discussion of the MET PCP-Combine tool and will practice running it directly on the command line.

PCP-Combine Functionality

The PCP-Combine tool is used (if needed) to add, subtract, sum or derive accumulated field values, most commonly 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 Data 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).
  [-vld_thresh n] Overrides the default required ratio of valid data (1) (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.