# CTM\_OCEAN\_CHEM settings vs SMOKE Ocean Cl2 emissions

**URL:** <https://forum.cmascenter.org/t/ctm-ocean-chem-settings-vs-smoke-ocean-cl2-emissions/5982>\
**Category:** CMAQ\
**Tags:** smoke\
**Created:** [September 4, 2025, 2:59pm UTC](https://forum.cmascenter.org/t/ctm-ocean-chem-settings-vs-smoke-ocean-cl2-emissions/5982 "2025-09-04T14:59:12Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![hosok004](https://avatars.discourse-cdn.com/v4/letter/h/9f8e36/32.png) [@hosok004](https://forum.cmascenter.org/u/hosok004)\
**Post date:** [September 4, 2025, 2:59pm UTC](https://forum.cmascenter.org/t/ctm-ocean-chem-settings-vs-smoke-ocean-cl2-emissions/5982/1 "2025-09-04T14:59:12Z")

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Hello,

I am running a CMAQv5.5 simulation for the 12US1 domain with the cracmmv2 mechanism and I had a quick question on whether I should set the cctm ocean chemistry settings to Y or N.

While preparing my emissions files with SMOKEv5.1, I included the sector “Ocean Cl2” in my sector merge to produce “merged\_nobeis\_norwc” files. Does this mean that sea spray aerosol emission are already included in my emission files, even if CTM\_OCEAN\_CHEM is set to N in my CCTM script? Or do I still need CTM\_OCEAN\_CHEM set to Y? Any help is appreciated. Thanks!

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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:** [September 5, 2025, 3:15pm UTC](https://forum.cmascenter.org/t/ctm-ocean-chem-settings-vs-smoke-ocean-cl2-emissions/5982/2 "2025-09-05T15:15:06Z")

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> [@hosok004](#):
>
> While preparing my emissions files with SMOKEv5.1, I included the sector “Ocean Cl2” in my sector merge to produce “merged\_nobeis\_norwc” files. Does this mean that sea spray aerosol emission are already included in my emission files, even if CTM\_OCEAN\_CHEM is set to N in my CCTM script?

No, sea spray aerosol emissions are calculated inline in CMAQ (if CTM\_OCEAN\_CHEM is set to Y) and not included in the “ocean cl2” sector processed by SMOKE. As the name implies, that sector only contains Cl2 emissions.

> Or do I still need CTM\_OCEAN\_CHEM set to Y

Yes, if you would like to include sea spray aerosol emissions, consider DMS and halocarbon chemistry, and enhanced O3 deposition over water, you will need to set `CTM_OCEAN_CHEM` to `Y`. Please see these sections of the user’s guide for more documentation:  
[Sea spray emissions](https://github.com/USEPA/CMAQ/blob/main/DOCS/Users_Guide/CMAQ_UG_ch06_model_configuration_options.md#Sea_Spray)  
[DMS and halocarbon emissions](https://github.com/USEPA/CMAQ/blob/main/DOCS/Users_Guide/CMAQ_UG_ch06_model_configuration_options.md#dimethyl-sulfide-dms-and-halocarbon-emissions)  
[Ocean file tutorial](https://github.com/USEPA/CMAQ/blob/main/DOCS/Users_Guide/Tutorials/CMAQ_UG_tutorial_oceanfile.md)

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**Author:** ![hosok004](https://avatars.discourse-cdn.com/v4/letter/h/9f8e36/32.png) [@hosok004](https://forum.cmascenter.org/u/hosok004)\
**Post date:** [September 5, 2025, 3:17pm UTC](https://forum.cmascenter.org/t/ctm-ocean-chem-settings-vs-smoke-ocean-cl2-emissions/5982/3 "2025-09-05T15:17:31Z")

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That makes sense. Thank you!

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**Author:** ![system](https://canada1.discourse-cdn.com/flex027/uploads/cmas/original/1X/9a72c78e529465c3f1053af404e3033b0875428c.png) [@system](https://forum.cmascenter.org/u/system)\
**Post date:** [September 12, 2025, 3:18pm UTC](https://forum.cmascenter.org/t/ctm-ocean-chem-settings-vs-smoke-ocean-cl2-emissions/5982/4 "2025-09-12T15:18:31Z")

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