Hi Leighton,
Sorry for my delay in replying - I was completely snowed-under last week.
ASAD is purely the chemical solver, and actually has nothing to do with emissions or the emissions routines. The tracers it considers are only those mentioned in the chemical mechanism as defined in ukca_chem_master.F90 or one of the other ukca_chem scheme definitions. You’re running offline oxidants so the scheme is rather basic.
The emissions routines consider both chemical and aerosol emissions and are not as well integrated as they should be. The logic is considered in ukca_emiss_mode_mod.F90, and ukca_emiss_ctl_mod.F90 is where ukca_add_emiss is called. In ukca_emiss_mod.F90 there is the routine ukca_emiss_update_mode which “Convert(s) total aerosol emission mass into mass and number for each mode.”
You might want to follow the logic from the call to ukca_emiss_ctl down from ukca_main to see how the tracers are treated. I’m sorry this is rather opaque - it’s a complicated set of routines as it deals with NetCDF formats, the associated metadata, and the fact that historically aerosol and chemical emissions were done very differently and this basically maintains that distinction and those differences. Essentially the aerosol tracers are considered there, but there are separate routines for these.
Best wishes,
Luke