# AERO process in Process Analysis

**URL:** <https://forum.cmascenter.org/t/aero-process-in-process-analysis/2868>\
**Category:** Chemistry and Aerosols\
**Created:** [December 9, 2021, 2:57pm UTC](https://forum.cmascenter.org/t/aero-process-in-process-analysis/2868 "2021-12-09T14:57:06Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![phy](https://avatars.discourse-cdn.com/v4/letter/p/35a633/32.png) [@phy](https://forum.cmascenter.org/u/phy)\
**Post date:** [December 9, 2021, 2:57pm UTC](https://forum.cmascenter.org/t/aero-process-in-process-analysis/2868/1 "2021-12-09T14:57:06Z")

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Hi, all!

I have some questions about process analysis in CMAQ version 5.3.1.

I think ‘AERO’ process is meaning contribution of gas-phase chemical reaction.

But I confirmed that the minimum value of ‘AERO\_ASO4I’ in my simulation represented negative value.

I want to know why negative value can be shown in AERO process.

And If my thinking (AERO process means gas-phase chemical reaction) is wrong, then how I can get contribution of gas phase chemical reaction in process analysis??

I hope that I get answers from you.

Thank you.

HyeonYeong Park

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**Author:** ![Ben\_Murphy](https://avatars.discourse-cdn.com/v4/letter/b/74df32/32.png) [@Ben\_Murphy](https://forum.cmascenter.org/u/Ben_Murphy)\
**Post date:** [January 3, 2022, 4:22pm UTC](https://forum.cmascenter.org/t/aero-process-in-process-analysis/2868/2 "2022-01-03T16:22:04Z")

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Hi HyeonYeong,

There was a bug in process analysis for aerosols introduced in v5.3. It is resolved in v5.3.3 – see Release Note 15 here ([CMAQ/CMAQv5.3.3\_bugfixes.md at 5.3.3+ · USEPA/CMAQ · GitHub](https://github.com/USEPA/CMAQ/blob/5.3.3%2B/DOCS/Release_Notes/CMAQv5.3.3_bugfixes.md)).  
Do you still get negative values with this corrected version?

Best wishes,  
Ben Murphy

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**Author:** ![phy](https://avatars.discourse-cdn.com/v4/letter/p/35a633/32.png) [@phy](https://forum.cmascenter.org/u/phy)\
**Post date:** [August 3, 2022, 9:58am UTC](https://forum.cmascenter.org/t/aero-process-in-process-analysis/2868/3 "2022-08-03T09:58:14Z")

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Hi, Dr. Murphy!

Thanks for your responses.

And I’m so sorry to answer about your responses too late… 😂

I conducted a small test with revised three source code files (sciproc.F, pa\_update.F, aero\_subs.F) to confirm appearance of negative values from ‘AERO\_ASO4I’.

Although, there is still negative values of ‘AERO\_ASO4I’, its absolute value was getting smaller than that from original version of CMAQ v5.3.1.

Thanks to your help for solving the problem 🙂

HyeonYeong Park