We now shift to a dicussion 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. It's 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") |
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| [-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, or -subtract command line option to indicate the operation to be performed. Each operation has its own set of required arguments.
