# How to get PM2.5\_TOT from CMAQ5.4-ISAM outputs by combine?

**URL:** <https://forum.cmascenter.org/t/how-to-get-pm2-5-tot-from-cmaq5-4-isam-outputs-by-combine/3831>\
**Category:** CMAQ-ISAM\
**Created:** [January 8, 2023, 3:08pm UTC](https://forum.cmascenter.org/t/how-to-get-pm2-5-tot-from-cmaq5-4-isam-outputs-by-combine/3831 "2023-01-08T15:08:58Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![AllenLu](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.cmascenter.org/allenlu/32/1350_2.png) [@AllenLu](https://forum.cmascenter.org/u/AllenLu)\
**Post date:** [January 8, 2023, 3:08pm UTC](https://forum.cmascenter.org/t/how-to-get-pm2-5-tot-from-cmaq5-4-isam-outputs-by-combine/3831/1 "2023-01-08T15:08:58Z")

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Hello，  
In CMAQ5.3.3, I’ve always used combine to calculate the PM2.5 concentrations, which is calculated as: ''PM25\_TOT=ATOTI[0]\*PM25AT[3]+ATOTJ[0]\*PM25AC[3]+ATOTK[0]\*PM25CO[3]" (chemical mechanism ‘cb6r3\_ae7\_aq’).  
But I can’t find PM25AT[3] PM25AC[3] and PM25CO[3] from CMAQ5.4 model outputs.  
How to get PM2.5\_TOT from CMAQ5.4-ISAM outputs?  
Thanks,  
Allen Lu.

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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:** [January 8, 2023, 5:29pm UTC](https://forum.cmascenter.org/t/how-to-get-pm2-5-tot-from-cmaq5-4-isam-outputs-by-combine/3831/2 "2023-01-08T17:29:44Z")

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Hello Allen,

if you wrote out the AELMO files and used the default setup to define their content, you should be able to use the following AELMO variables instead of the old APMDIAG variables in your ISAM PM25\_TOT calculations:

FPM25AIT instead of PM25AT  
FPM25ACC instead of PM25AC  
FPM25COR instead of PM25CO

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**Author:** ![AllenLu](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.cmascenter.org/allenlu/32/1350_2.png) [@AllenLu](https://forum.cmascenter.org/u/AllenLu)\
**Post date:** [January 9, 2023, 2:06am UTC](https://forum.cmascenter.org/t/how-to-get-pm2-5-tot-from-cmaq5-4-isam-outputs-by-combine/3831/3 "2023-01-09T02:06:07Z")

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Hello Hogrefe,  
I appreciate your prompt response. The problem has been solved.  
Thanks,  
Allen