CMAQ v5.3.3 UFP concentration and number

I am not sure my combine file for UFP (less than 0.1um) is right.
or Are there any other ways to calculate UFP concentration and its numbers?

UFP total = ATOTI, UFP number = NUMACC[1]

If you define ultrafine as diameter < 0.1 um, then you would need to determine how much of the aitken (I) + accumulation (J) modes are present below 0.1 um. NUMACC is the number of accumulation mode particles and ATOTI is the aitken mode mass. The PMDIAG output file currently computes the fraction of aitken, accumulation, and coarse modes below 1, 2.5, and 10 um. You could add a <0.1 cutoff as well. To implement it, take a look at aero_driver.F and the calculation and assignment of “fPM1” quantities as well as SUBROUTINE AERO_INLET in aero_subs.F for a template. @Ben_Murphy may have more suggestions.

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