I’ve been using the spec_def.conc file to aggregate PM2.5 and the ‘unspeciated’ portion, from CMAQv5.0.2 output. ‘PM25_UNSPEC1’ is defined in terms of PM25_TOT and aggregated PM25 categories (e.g. PM25_SO4, PM25_EC, etc.). It is not defined in terms of actual CMAQ output variables. However, it should still be possible to rearrange the output variables and create an exact ‘formula’ for ‘PM25_UNSPEC1’. The problem that I am running into is that when I do this, (1) I find some double-counting in the existing definitions, and (2) I cannot recreate PM25_UNSPEC1 directly from output variables to match the PM25_UNSPEC1 defined in terms of aggregated PM25 categories.
Is it proper to attempt to do this? If so, then some of PM25_UNSPEC1 is composed of CMAQ output variables which are actual species. Is it correct to assume that these variables aren’t ‘unspeciated’ or ‘other’ and can be used for comparison to speciated data (assuming these species are reported in the data)? This would have the effect of reducing the amount of PM25 reported as ‘unspeciated’ from CMAQ output. Has anyone done this before or created a ‘formula’ for PM25_UNSPEC1?
That is my primary question, but here are specific details about the double-counting in the spec_def.conc file (attached and available on github):
In the PM25_TOT definition, PM25 is the sum of ATOTI, J, and K. In these definitions, all the SOA species are added as OM without any scaling factors. In the calculation of PM_UNSPEC1, the SOA species are subtracted out of PM25_TOT with scaling factors applied. (As part of AOCIJ, which is part of PM25_OC). This seems to mean some >0 fraction of the SOA species are part of ‘PM25_UNSPEC1’, which would inflates the amount of ‘other’ when aggregating PM25 this way.
For the calculation of ‘PM25_UNSPEC1’, ASOILJ is subtracted out of PM25_TOT (as part of PM25_SOIL). However, ASOILJ is defined in the spec_def file and includes multiplicative factors >1 on its constituent species (AALJ, ASIJ, ACAJ, AFEJ, ATIJ). When these species are added to ATOTJ, they have a factor of 1. This seems to ‘double count’ these variables in PM25_SOIL, since they are added with a factor of 1 in the PM25_TOT definition, but added with factors >1 in the PM25_SOIL definition. If that’s the case, this would also artificially decrease the amount of ‘other’ in PM25 when it is aggregated this way. Is this the intended way to calculate PM25 ‘unspeciated’?
I appreciate any feedback to this wordy post!
spec_def.conc.txt (8.7 KB)