Specifies either clm4_0, clm4_5, or clm5_0 physics Root directory of CLM source distribution (directory above CLM configure). Component framework interface to use (Model Coupling Toolkit, or Earth System Modeling Framework) User source directories to prepend to the filepath. Multiple directories are specified as a comma separated list with no embedded white space. Normally this is SourceMods/src.clm in your case. User specified CPP defines to append to Makefile defaults. Note: It's recommended to use configure options to set standard CPP values rather than defining them here.