# CMAQ STM calculation method and reference
**URL:** https://forum.cmascenter.org/t/cmaq-stm-calculation-method-and-reference/1972
**Category:** CMAQ
**Created:** [December 8, 2020, 4:27pm UTC](https://forum.cmascenter.org/t/cmaq-stm-calculation-method-and-reference/1972 "2020-12-08T16:27:42Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@phy](https://forum.cmascenter.org/u/phy)
#### Post date: [December 8, 2020, 4:27pm UTC](https://forum.cmascenter.org/t/cmaq-stm-calculation-method-and-reference/1972/1 "2020-12-08T16:27:42Z")
Hi, all!
I’m writing a paper about STM module in CMAQv5.3.1.
However, although I checked STM source file STM\_MODULE.F, I couldn’t find some references about calculating STM. Also, I want to know meaning of ‘mscor’ in STM\_MODULE.F.
If you guys know references about calculating STM, please let me know.
Thanks
HyeonYeong Park
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### Author:  [@lizadams](https://forum.cmascenter.org/u/lizadams)
#### Post date: [December 8, 2020, 4:45pm UTC](https://forum.cmascenter.org/t/cmaq-stm-calculation-method-and-reference/1972/2 "2020-12-08T16:45:52Z")
There is some information here:
>
and
> **[CMAQv5.0 Sulfur Chemistry - CMASWIKI](https://www.airqualitymodeling.org/index.php/CMAQv5.0_Sulfur_Chemistry)**
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### Author:  [@phy](https://forum.cmascenter.org/u/phy)
#### Post date: [December 9, 2020, 3:22am UTC](https://forum.cmascenter.org/t/cmaq-stm-calculation-method-and-reference/1972/3 "2020-12-09T03:22:54Z")
I’m really appreciate for your replying for my question 🙂
But I have one more question.
Can I call STM species such as ‘ASO4AQH2O2J’, ‘ASO4AQFEMNJ’ etc. ‘counter species’???