Hi,
It looks like this variable is called in WRF/dyn_em/module_big_step_utilities.F. You can do a search for 'w_damping' in that file. You can put in a print statement inside the "IF" loop to see if it's printed out. If you add this, you'll need to recompile the code, but you do not need to clean or reconfigure the code. Just simply recompile wrf. Then after you run the simulation, your print statements should be in your out files (e.g., one of the rsl.out.* files).