# Question about CMAQ-DDM v5.2 output variables

**URL:** <https://forum.cmascenter.org/t/question-about-cmaq-ddm-v5-2-output-variables/982>\
**Category:** Post-processing\
**Created:** [September 28, 2019, 6:25am UTC](https://forum.cmascenter.org/t/question-about-cmaq-ddm-v5-2-output-variables/982 "2019-09-28T06:25:06Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![Ryan](https://avatars.discourse-cdn.com/v4/letter/r/a8b319/32.png) [@Ryan](https://forum.cmascenter.org/u/Ryan)\
**Post date:** [September 28, 2019, 6:25am UTC](https://forum.cmascenter.org/t/question-about-cmaq-ddm-v5-2-output-variables/982/1 "2019-09-28T06:25:06Z")

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Hi all,  
Recently I am working for tracking ozone sensitivity through NOx and VOCs by using CMAQ-DDM. And I am confused about the meaning of variables in the ASENS file. I found that all species were classified to 2 types (one was O3\_ENS, and another one was O3\_ESX).  
May I ask what the specific meaning about these variables ?  
Besides, if I want to track ozone sensitivity through NOx and VOCs by using CMAQ-DDM, how can I set the sensinput.cmas.dat ?

Best,  
Ryan

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**Author:** ![Ryan](https://avatars.discourse-cdn.com/v4/letter/r/a8b319/32.png) [@Ryan](https://forum.cmascenter.org/u/Ryan)\
**Post date:** [September 29, 2019, 5:12am UTC](https://forum.cmascenter.org/t/question-about-cmaq-ddm-v5-2-output-variables/982/2 "2019-09-29T05:12:46Z")

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@tlspero@lizadams@bbaek@hogrefe.christian @cgnolte

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**Author:** ![lizadams](https://avatars.discourse-cdn.com/v4/letter/l/49beb7/32.png) [@lizadams](https://forum.cmascenter.org/u/lizadams)\
**Post date:** [September 29, 2019, 12:59pm UTC](https://forum.cmascenter.org/t/question-about-cmaq-ddm-v5-2-output-variables/982/3 "2019-09-29T12:59:47Z")

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Hi Ryan,

The tag ENX is defined in the sensinput.cmas.dat  
It was defined as the sensitivity of ozone to NO and NO2.

The tag ESX is defined in the sensinput.cmas.dat as the sensitivity of ozone to SO2.

https://www.airqualitymodeling.org/index.php/CMAQ\_version\_5.2\_DDM\_Technical\_Documentation

There was another issue in this forum that describes the setup for determining the sensitivity to NOX from the transportation sector that may be helpful.  
[https://forum.cmascenter.org/t/cmaq-ddm-3d-sensinput-file-setting-about-ddm3d-es-emissions-split-into-categories-sensitivity/632](https://forum.cmascenter.org/t/cmaq-ddm-3d-sensinput-file-setting-about-ddm3d-es-emissions-split-into-categories-sensitivity/632)

Liz

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**Author:** ![Ryan](https://avatars.discourse-cdn.com/v4/letter/r/a8b319/32.png) [@Ryan](https://forum.cmascenter.org/u/Ryan)\
**Post date:** [September 29, 2019, 6:16pm UTC](https://forum.cmascenter.org/t/question-about-cmaq-ddm-v5-2-output-variables/982/4 "2019-09-29T18:16:27Z")

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Hi Liz,  
Thanks for the response. May I ask how to set the sensitivity of ozone to VOCs  
and NOx in the sensinput.cmas.dat ? Should I tag all VOCs species in the sensinput.cmas.dat as a type of EVOCX ?

Best,  
Ryan

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**Author:** ![lizadams](https://avatars.discourse-cdn.com/v4/letter/l/49beb7/32.png) [@lizadams](https://forum.cmascenter.org/u/lizadams)\
**Post date:** [September 29, 2019, 6:54pm UTC](https://forum.cmascenter.org/t/question-about-cmaq-ddm-v5-2-output-variables/982/5 "2019-09-29T18:54:31Z")

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Hi Ryan,  
The following section of the user manual indicates that there are 21 species for VOC if you are using the following mechanism: CB6R3 (see OZ\_DEFN.F)

> <https://github.com/USEPA/CMAQ/blob/master/DOCS/Users_Guide/CMAQ_UG_ch11_ISAM.md>

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<div class="post-metadata">

**Author:** ![Ryan](https://avatars.discourse-cdn.com/v4/letter/r/a8b319/32.png) [@Ryan](https://forum.cmascenter.org/u/Ryan)\
**Post date:** [September 29, 2019, 7:12pm UTC](https://forum.cmascenter.org/t/question-about-cmaq-ddm-v5-2-output-variables/982/6 "2019-09-29T19:12:03Z")

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Hi Liz,  
Thanks for the response. Due to the limitation of emission inventory, I only have one area emission source for the CMAQ-ISAM model. So can I calculate the the ozone formation from VOCs  
and NOx separate by only using one area emission source ？

Best,  
Ryan

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**Author:** ![lizadams](https://avatars.discourse-cdn.com/v4/letter/l/49beb7/32.png) [@lizadams](https://forum.cmascenter.org/u/lizadams)\
**Post date:** [September 29, 2019, 7:35pm UTC](https://forum.cmascenter.org/t/question-about-cmaq-ddm-v5-2-output-variables/982/7 "2019-09-29T19:35:26Z")

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> [@Ryan](#):
>
> emission inventory, I only have one area emission source for the CMAQ-ISAM model

Hi Ryan,  
Do you mean you only have one emission source, and that it is an area source, ie. that you have no point sources in your emissions inventory?  
I believe you could still do the ISAM to determine the amount of ozone due to VOC from a specific region within your domain.

> <https://github.com/USEPA/CMAQ/blob/main/DOCS/Users_Guide/CMAQ_UG_ch11_ISAM.md>

How to specify the region that is adjusted for scaling:

> <https://github.com/lizadams/CMAQ/blob/main/DOCS/Users_Guide/Tutorials/CMAQ_UG_tutorial_emissions.md#11-apply-scaling-with-spatial-dependence>

A cool example of calculating the Ozone due to wildfire emissions:  
[https://ofmpub.epa.gov/rsig/rsigserver?cmaq\_application/public/isam.html](https://ofmpub.epa.gov/rsig/rsigserver?cmaq_application/public/isam.html)