I am using the CMAQ system and need to turn off horizontal transport. I’m unsure where the relevant settings are, whether in input files or source code. I want a reliable way to disable it without causing errors or affecting system stability. I also wonder if recompilation is needed and what precautions to take. Please provide guidance. Thanks.
I believe you can turn off transport of individual species by editing the TRNS column of the associated species namelist file, e.g., here. This would not require compilation.
If you want to turn off advection entirely, then you would need to edit sciproc.F and comment out the call to HADV, and ZADV if desired. These modifications would require recompilation to take effect.