How to add other substances to CH4 simulation?

[Liyl2]

Your name

Yali LI

Your affiliation

Southern University of Science and Technology

Please provide a clear and concise description of your question or discussion topic.

I am using GCClassic 14.0.2，and when I choose “CH4 simulation” simulation type and the compilation uses the fullchem mechanism (I don't know if it is correct but it outputs normally) and it runs very efficiently. I would like to ask two questions about this:

1. Is the chemical mechanism of CH4 simulation only call CH4 related in fullchem mechanism, there is no separate mechanism (similar to custom) in GEOS-Chem/KPP/?
2. Can I add the substance I want to simulate (e.g. HFC-134a) in the CH4 simulation? I have now added HFC-134a to the custom mechanism and successfully output the HFC-134a concentration, but the output is slow and I would like to improve the efficiency of the run.
   Looking forward to your reply, thanks!

[msulprizio]

Thanks for writing @Liyl2. We recommend that you update to the latest release of GEOS-Chem if possible. In GEOS-Chem 14.1.0 we introduced the carbon simulation which includes CO2, CO, CH4, and OCS. It can be run with all four species or in single species mode. Since version 14.1.0, several fixes have bee made to the carbon simulation with more fixes in the pipeline (especially for running the carbon simulation in GCHP). Please also note that in 14.6.0, we're planning on retiring the CH4 (and CO2 and tagCO2) simulation in favor of the carbon simulation.

The carbon simulation uses the KPP solver for chemistry rather than individual chemistry routines hardcoded in the fortran modules. For example the current CH4 simulation performs chemistry via the CHEMCH4 routine in global_ch4_mod.F90. (It doesn't actually use KPP, even though the build log will indicate that KPP has been built with the fullchem mechanism.)

The carbon simulation in KPP will also make it more flexible for you to add more species. This can be done by modifying the carbon.eqn file and adding any new species to the GEOS-Chem species database.