# About Ozone diurnal

**URL:** <https://forum.cmascenter.org/t/about-ozone-diurnal/2219>\
**Category:** CMAQ\
**Tags:** cmaqsmoke\
**Created:** [April 5, 2021, 5:49am UTC](https://forum.cmascenter.org/t/about-ozone-diurnal/2219 "2021-04-05T05:49:35Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![SharMM](https://avatars.discourse-cdn.com/v4/letter/s/96bed5/32.png) [@SharMM](https://forum.cmascenter.org/u/SharMM)\
**Post date:** [April 5, 2021, 5:49am UTC](https://forum.cmascenter.org/t/about-ozone-diurnal/2219/1 "2021-04-05T05:49:35Z")

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Hi,  
I have a question about the CMAQ 5.3.2 output, diurnal profile of O3 seems strange, i see high concentration during the night while day time is low. It seems like there is a shift in 8-10 hours. I am wondering if I did any mistake in CMAQ/SMOKE settings. Can anyone suggest what could be the  
issue? Thanks a lot.

|Hour|O3|  
|0|42.42|  
|1|42.69|  
|2|40.55|  
|3|36.59|  
|4|31.08|  
|5|28.28|  
|6|29.00|  
|7|31.55|  
|8|25.56|  
|9|28.66|  
|10|25.61|  
|11|25.73|  
|12|26.76|  
|13|24.60|  
|14|29.01|  
|15|31.13|  
|16|32.27|  
|17|33.35|  
|18|34.77|  
|19|36.34|  
|20|36.85|  
|21|37.42|  
|22|37.59|  
|23|38.10|

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<div class="post-metadata">

**Author:** ![Hun](https://avatars.discourse-cdn.com/v4/letter/h/cab0a1/32.png) [@Hun](https://forum.cmascenter.org/u/Hun)\
**Post date:** [April 5, 2021, 6:17am UTC](https://forum.cmascenter.org/t/about-ozone-diurnal/2219/2 "2021-04-05T06:17:08Z")

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Did you check timezone?

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**Author:** ![SharMM](https://avatars.discourse-cdn.com/v4/letter/s/96bed5/32.png) [@SharMM](https://forum.cmascenter.org/u/SharMM)\
**Post date:** [April 5, 2021, 2:45pm UTC](https://forum.cmascenter.org/t/about-ozone-diurnal/2219/3 "2021-04-05T14:45:04Z")

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Thanks for the quick response. You mean while running SMOKE? Where is that setting?

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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:** [April 5, 2021, 8:07pm UTC](https://forum.cmascenter.org/t/about-ozone-diurnal/2219/4 "2021-04-05T20:07:54Z")

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Please note the CMAQ output is UTC standard time. You need to shift the output timezone to the region which you are investigating. For example, the timezone for the UK in UTC is UTC+1 while for China it is UTC+8. It means that the CMAQ output at 0:00 am is 01:00 am in UK and 08:00 am in China.

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**Author:** ![SharMM](https://avatars.discourse-cdn.com/v4/letter/s/96bed5/32.png) [@SharMM](https://forum.cmascenter.org/u/SharMM)\
**Post date:** [April 6, 2021, 3:17am UTC](https://forum.cmascenter.org/t/about-ozone-diurnal/2219/5 "2021-04-06T03:17:26Z")

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Thank you very much for the useful info