# How to calculate PM25\_TOT/PM25 Concentration from CMAQv5.3.2-ISAM results?

**URL:** <https://forum.cmascenter.org/t/how-to-calculate-pm25-tot-pm25-concentration-from-cmaqv5-3-2-isam-results/2109>\
**Category:** CMAQ-ISAM\
**Created:** [February 22, 2021, 2:00pm UTC](https://forum.cmascenter.org/t/how-to-calculate-pm25-tot-pm25-concentration-from-cmaqv5-3-2-isam-results/2109 "2021-02-22T14:00:33Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Catalyst2682](https://avatars.discourse-cdn.com/v4/letter/c/a6a055/32.png) [@Catalyst2682](https://forum.cmascenter.org/u/Catalyst2682)\
**Post date:** [February 22, 2021, 2:00pm UTC](https://forum.cmascenter.org/t/how-to-calculate-pm25-tot-pm25-concentration-from-cmaqv5-3-2-isam-results/2109/1 "2021-02-22T14:00:33Z")

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Dear @sergey @hogrefe.christian,

I have successfully run ISAM using CMAQv5.3.2 with saprc07tic\_aero6 mechanism. Please, how do I calculate the concentration of PM25\_TOT or PM25 from my results? I don’t know which species definition to be used as this is different from the normal CMAQ calculation.

Thanks in anticipation and kind regards.

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**Author:** ![hogrefe.christian](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@hogrefe.christian](https://forum.cmascenter.org/u/hogrefe.christian)\
**Post date:** [February 22, 2021, 3:26pm UTC](https://forum.cmascenter.org/t/how-to-calculate-pm25-tot-pm25-concentration-from-cmaqv5-3-2-isam-results/2109/2 "2021-02-22T15:26:59Z")

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As noted by @ykaore [in posts 3 and 9 of the other thread that question came up](https://forum.cmascenter.org/t/different-base-pm2-5-concentration-when-applied-regional-file-in-cmaqv5-3-2-isam/1990/9), you’ll have to work with the Aitken and accumulation mode species provided by your ISAM run.

Simply put, sum up all the PM species provided in your ISAM output file and multiply the Aitken mode species with PM25AT and the accumulation mode species with PM25AC. Post 9 contains an example how this was done in @ykaore’s case. Note that this will be different from the standard PM25 calculation using the concentration output files because coarse mode species aren’t included in ISAM. @sergey may have additional thoughts.

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**Author:** ![ykaore](https://avatars.discourse-cdn.com/v4/letter/y/ce73a5/32.png) [@ykaore](https://forum.cmascenter.org/u/ykaore)\
**Post date:** [February 22, 2021, 3:53pm UTC](https://forum.cmascenter.org/t/how-to-calculate-pm25-tot-pm25-concentration-from-cmaqv5-3-2-isam-results/2109/3 "2021-02-22T15:53:43Z")

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Additionally @Catalyst2682, you can also compare the PM25\_TOT from ACONC or COMBINE files and the values that you are gonna calculate using ISAM output in order to have a look if the differences are inegligible or not (in this case, to have look at the influence of coarse mode in your PM25\_TOT).

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**Author:** ![Catalyst2682](https://avatars.discourse-cdn.com/v4/letter/c/a6a055/32.png) [@Catalyst2682](https://forum.cmascenter.org/u/Catalyst2682)\
**Post date:** [February 22, 2021, 4:13pm UTC](https://forum.cmascenter.org/t/how-to-calculate-pm25-tot-pm25-concentration-from-cmaqv5-3-2-isam-results/2109/4 "2021-02-22T16:13:34Z")

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@hogrefe.christian.

Thanks for your response. I’ll follow @ykaore’s method as I’ve been in contact with her on this. I only want to know if there’s an alternative to it.

Catalyst

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**Author:** ![Catalyst2682](https://avatars.discourse-cdn.com/v4/letter/c/a6a055/32.png) [@Catalyst2682](https://forum.cmascenter.org/u/Catalyst2682)\
**Post date:** [February 22, 2021, 4:15pm UTC](https://forum.cmascenter.org/t/how-to-calculate-pm25-tot-pm25-concentration-from-cmaqv5-3-2-isam-results/2109/5 "2021-02-22T16:15:19Z")

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@ykaore,

Yes, I’ll do and compare the results as suggested by you. I’ll feed you back.

Thanks and kind regards,

Catalyst