In order to use the GrADS tools, you will need the GrADS fonts and maps data sets
and may need to set some environment variables. For more information, see:
http://cola.gmu.edu/grads/downloads.php
grads is built for Intel macOS and so requires Rosetta 2 to be installed.
You can install Rosetta 2 with:
softwareupdate --install-rosetta --agree-to-license
Note that it is very difficult to remove Rosetta 2 once it is installed.