I am trying to create BC/IC for CMAQ from a global model (AM3) which has a single SOA species to represent Secondary Organic Aerosol, but I am not sure how to divide the single global model SOA species into multiple CMAQ cb6r3_ae7_aq aerosol species in a CONUS domain.
We cannot provide specific mappings for all possible models, but here are some things to consider. Generally, you should map the same precursor system to the same precursor system. For example, if the SOA species is from monoterpene oxidation, then map to the monoterpene SOA set in CMAQ. Second, if there is an assumed volatility in one model, it should be mapped to the same volatility in CMAQ. C* is a measure of volatility with C*=0.1ug/m3 effectively nonvolatile if you need a nonvolatile mapping. To get a better description of aero7 species, see https://www.epa.gov/cmaq/how-cite-cmaq (Organic Aerosol tab) and https://github.com/USEPA/CMAQ/blob/master/DOCS/Release_Notes/aero7_overview.md. Pye et al. 2017 ACP, Murphy et al. 2017 ACP, and the aero7 release notes should define all species. We also include species descriptions in the code (CCTM/src/MECHS/mechanism_information; https://github.com/USEPA/CMAQ/blob/master/CCTM/src/MECHS/mechanism_information/cb6r3_ae7_aq/AE7_species_table.md)