The Cheyenne environment supports the use of NCAR Command Language (NCL) both interactively and in batch mode to analyze and visualize data.
As described below, to use NCL in the Cheyenne environment you will log in to Cheyenne or Casper, then:
Follow the instructions below to get started, and customize the scripts and commands as necessary to work with your own data.
See the NCL web site for complete documentation of the language's extensive analysis and visualization capabilities.
See the NCL Applications page for links to hundreds of complete NCL scripts that you can download and modify as needed.
Interactive useTo start an interactive window from which to modify and execute NCL scripts, log in to Cheyenne.
Start a job on Casper as described in this documentation. When your job starts, load the default module for NCL.
Modify your NCL script if necessary using a UNIX editor, and execute it as shown here, substituting the name of your own NCL script for script_name.ncl.
Submitting a batch scriptIf you expect running your NCL script to take longer than you would want to work interactively — overnight, for example — submit your NCL script in a batch job so it can run unattended. See Starting jobs on Casper nodes for batch job script examples and other details. When your batch script is ready, use the qsub command and the name of your script file.
You might also find command files useful for performing a number of related NCL tasks in parallel. See this documentation for information about command files. Visualization examplesExample 1Make an NCL script file named contour_ts_line.ncl using the sample script below. When you run it on Casper, it will create a simple line contour plot (Figure 1) using a sample CMIP5 NetCDF data file in the /glade/u/sampledata/ncl/CESM/CAM5 directory. The output to your working directory will be a graphic file called contour_ts_line.png.
Sample NCL script
Example 2Using a different script, you can create a more interesting visualization with the data that was used in the first example. Make an NCL script file named contour_ts_color.ncl using the sample script below. When you run it on Casper, the output to your working directory will be a color-filled contour (Figure 2) called contour_ts_color.png.
Sample NCL script
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