Is CMAQ-ISAM possible to tag for Particle Number variable (NUMATN, NUMACC, or NUMCOR)?

I am curious if CMAQ-ISAM can tag for particle numbers.

In the isam_control.txt file,
I can choose only 9 options.
e.g. !!! Choose any/all from the list of nine: SULFATE, NITRATE, AMMONIUM, EC, OC, VOC, PM25_IONS, OZONE, CHLORINE

Should I change SA_DEFN.F to tag a new variable?

Best regards,


Unfortunately, number and surface area are currently not included, and it is not clear how the ISAM source-tagging approach could be extended to handle these metrics since they are not conserved like mass is.

For example, if a small particle and large particle from to sources collide, what is the source allocation of the resulting particle? Surface area would in theory be more tractable since it is a continuous quantity, but it would be difficult to determine how one thinks about particle morphology and source distribution. It would not be a very meaningful prediction at this point.

My recommendation (if you have a limited number of sources you are considering) would be to zero out each source of concern and quantify the impact on particle number.

Best wishes,

1 Like

Hello Ben,

Thank you for your comment and recommendation.
From my understanding, it is the BFM method, right?
i.e. running CMAQ with and without each source.

Best regards,

That’s absolutely right. I think brute force is the best way to go for this question at the moment.