METplus Practical Session Guide (Version 5.0) | MET Tool: PCP-Combine > Derive Command

While the PCP-Combine -add and -subtract commands compute exactly one output field of data, the -derive command can compute multiple output fields in a single run. This command reads data from one or more input files and derives the output fields requested on the command line (sum, min, max, range, mean, stdev, vld_count).

Run the following command to derive several summary metrics for both the 10-meter U and V wind components:

pcp_combine -derive min,max,mean,stdev \
${METPLUS_DATA}/met_test/data/sample_fcst/2005080700/wrfprs_ruc13_*.tm00_G212 \
-field 'name="UGRD"; level="Z10";' \
-field 'name="VGRD"; level="Z10";' \

In the above example, we used a wildcard to list multiple input file names.  And we used the -field command line option twice to specify two input fields.  For each input field, PCP-Combine loops over the input files, derives the requested metrics, and writes them to the output NetCDF file.  Run ncview to visualize this output:

ncview &

This output file contains 8 variables: 2 input fields * 4 metrics. Note the output variable names the tool chose.  You can still override those names using the -name command line argument, but you would have to specify a comma-separated list of 8 names, one for each output variable.