Hello, I had a question regarding CCTM science option settings when using agricultural emissions generated from the EQUATES project SMOKE input files. From what I understand, these files only include livestock NH3 emissions and exclude fertilizer NH3, with the expectation that the user calculates NH3_fert with the in-line CTM_ABFLUX science option in CMAQ.
Does this mean that the CTM_BIDI_FERT_NH3 science option should be set to N instead of the default Y when using EQUATES emission files (since there is no NH3_fert in the input emission files)? Any advice is appreciated. Thanks!
README_EQUATES_09Dec2021.txt (22.8 KB)
Hello @hosok004 ,
thank you for your question.
While the CTM_BIDI_FERT_NH3 flag is indeed present in the CMAQv5.5 run scripts, it actually is no longer being read in by that version of the code and does not have any effect. When CTM_ABFLUX is activated in CMAQ by setting this option to T, the code will look for variable NH3_FERT in emission input files, and if that variable is found, subtract it from the emissions being read in for model species NH3. If your emission files do not have variable NH3_FERT, or if its value is 0, nothing will be subtracted.
We plan to update our run scripts in future releases to remove this obsolete environment variable `CTM_BIDI_FERT_NH3` and also update our documentation accordingly.
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Thanks for your help! Just to clarify, does it make any difference if CTM_ABFLUX is set to “T” versus “Y”? I’ve noticed that some of the default CCTM science options are set to T, but the comments beside them list [Y/N] as the controls.
No, using “T” vs. “Y” (or “F” vs. “N”) will not cause any differences in behavior. “T” and “Y” both evaluate to TRUE and “F” and “N” both evaluate to FALSE.
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Great, thanks for your help!