<p>Generally, spin up is necessary. To give context, look at how the model initializes. Does that look anything like a real chemical field? If you don’t have the eye for such things, examine the RMSE or other error metrics and compare them to other studies. Odds are, probably not. So you have to supply the model with emissions data and give a long enough period for it to seem at least plausible.</p>
<p>When I was using WRF-Chem to simulate <span class="math-container">$\ce{O3}$</span>, I used a couple days for the emission of <span class="math-container">$\ce{NO_x}$</span> to be somewhat representative.</p>

CC BY-SA 4.0
2022-01-22T10:34:45.713Z
I am new to running the WRF-Chem model, so this question maybe a little elementary. Therefore, I wanted to ask that to perform an year-long simulation of certain chemical species for 2019, would I have to provide the emissions for 2019 or for example, 2015 would suffice. I am assuming that the WRF-Chem model will be able to interpolate the emissions to 2019. The reason I am asking this question is because EDGAR/ECLIPSE emissions are available for 2015 and not 2019.
Sujai Banerji
CC BY-SA 4.0
2022-01-15T06:56:48.897Z
2022-01-15T06:56:48.897Z
BarocliniCplusplus
<p>For example, I am interested in making a simulation for some chemical species for 2019. I am planning to provide NCEP/GDAS FNL meteorological data at 0.25 degree and CAM-Chem chemical boundary layer. I want to know what time period of meteorological data and chemical boundary layer should I provide for my simulation?</p>

CC BY-SA 4.0
2022-01-10T01:39:26.773Z
Depending on the initial conditions you use and the meteorological event involved, I've found it takes at least 2-3 days of spin-up for the chemical conditions to stabilize in regional CTMs.
f.thorpe
CC BY-SA 4.0
2022-01-10T07:55:38.930Z
I am trying to do an year-long simulation. I do not think 2-3 days of spin-up would be enough for the chemical conditions to stabilize in regional CTMs. What I am confused about is that if I am trying to do a simulation for 2019, do I have to provide meteorological data and chemical boundary layer for 2019 and/or let us say, December 2018?
Sujai Banerji
CC BY-SA 4.0
2022-01-10T08:06:48.483Z
Meteorology usually takes longer to spin up than chemistry.  Once your chemical boundary conditions wash over your entire domain... it's spun.  If winds are stagnant it could take more than 3 days but it doesn't really matter how long your simulation is.   Since you are using WRF-CHEM and they are coupled, maybe you take 5 days (e.g. start at Dec 27) but that's more for the meteorology than the chemistry.
f.thorpe
CC BY-SA 4.0
2022-01-10T11:52:24.257Z
So, if I understand you correctly, 2-3 days of chemical boundary conditions and around 5 days of meteorological data towards the end of December 2018 should be fine for a year-long simulation of chemical species for 2019?
Sujai Banerji
CC BY-SA 4.0
2022-01-10T22:32:44.873Z
If you are looking at typical air quality products like ozone and aerosols, etc. then the chemistry is quick and transport dominates.  If you are modeling GHGs and other long-lived pollutants, then you would need a much longer chemical spin-up (or really good initial conditions). If you have a large domain (e.g. continental) you might need more days so the transport can flush out the initial conditions from the entire domain. 
 https://forum.mmm.ucar.edu/phpBB3/viewtopic.php?t=9894  https://wiki.harvard.edu/confluence/pages/viewpage.action?pageId=228526205#WRF/WRFChem-WRF-Chem:APM2.5example
f.thorpe
CC BY-SA 4.0
2022-01-10T22:35:37.407Z
If you really want to be conservative you could do a full week of Met/Chem spinup.  Then noone can question the first dew days of your 2019 results.
f.thorpe
CC BY-SA 4.0
2022-01-22T10:32:19.403Z
I am new to running the WRF-Chem model, so this question maybe a little too elementary. Therefore, I wanted to ask that to perform an year-long simulation of certain chemical species for 2019, would I have to provide the emissions for 2019 or for example, 2015 would suffice. I am assuming that the WRF-Chem model will be able to interpolate the emissions to 2019. The reason I am asking this question is because EDGAR/ECLIPSE emissions are available for 2015 and not 2019.
Sujai Banerji
CC BY-SA 4.0
2022-01-23T01:10:51.070Z
That's a separate question, you should post that as a new question.  An emissions modeling platform often uses information from various years depending on availability.
f.thorpe
CC BY-SA 4.0
2022-01-23T22:47:49.560Z
Thanks for the advice. I have also asked it as an independent question now.
Sujai Banerji
<models><climate-models><atmosphere-modelling><wrf><wrf-chem>
Is spin-up really required to run the WRF-Chem model and if so, what determines the time period of the spin-up?
Sujai Banerji
# Is spin-up really required to run the WRF-Chem model and if so, what determines the time period of the spin-up?

(Asked by: username_0 on 2022-01-09)

For example, I am interested in making a simulation for some chemical species for 2019. I am planning to provide NCEP/GDAS FNL meteorological data at 0.25 degree and CAM-Chem chemical boundary layer. I want to know what time period of meteorological data and chemical boundary layer should I provide for my simulation?

**Tags:** models, climate-models, atmosphere-modelling, wrf, wrf-chem

> **Comments:**
> **username_1**: Depending on the initial conditions you use and the meteorological event involved, I've found it takes at least 2-3 days of spin-up for the chemical conditions to stabilize in regional CTMs.  
> **username_0**: I am trying to do an year-long simulation. I do not think 2-3 days of spin-up would be enough for the chemical conditions to stabilize in regional CTMs. What I am confused about is that if I am trying to do a simulation for 2019, do I have to provide meteorological data and chemical boundary layer for 2019 and/or let us say, December 2018?  
> **username_1**: Meteorology usually takes longer to spin up than chemistry.  Once your chemical boundary conditions wash over your entire domain... it's spun.  If winds are stagnant it could take more than 3 days but it doesn't really matter how long your simulation is.   Since you are using WRF-CHEM and they are coupled, maybe you take 5 days (e.g. start at Dec 27) but that's more for the meteorology than the chemistry.  
> **username_0**: So, if I understand you correctly, 2-3 days of chemical boundary conditions and around 5 days of meteorological data towards the end of December 2018 should be fine for a year-long simulation of chemical species for 2019?  
> **username_1**: If you are looking at typical air quality products like ozone and aerosols, etc. then the chemistry is quick and transport dominates.  If you are modeling GHGs and other long-lived pollutants, then you would need a much longer chemical spin-up (or really good initial conditions). If you have a large domain (e.g. continental) you might need more days so the transport can flush out the initial conditions from the entire domain.   https://forum.mmm.ucar.edu/phpBB3/viewtopic.php?t=9894  https://wiki.harvard.edu/confluence/pages/viewpage.action?pageId=228526205#WRF/WRFChem-WRF-Chem:APM2.5example  
> **username_1**: If you really want to be conservative you could do a full week of Met/Chem spinup.  Then noone can question the first dew days of your 2019 results.  
> **username_0**: I am new to running the WRF-Chem model, so this question maybe a little too elementary. Therefore, I wanted to ask that to perform an year-long simulation of certain chemical species for 2019, would I have to provide the emissions for 2019 or for example, 2015 would suffice. I am assuming that the WRF-Chem model will be able to interpolate the emissions to 2019. The reason I am asking this question is because EDGAR/ECLIPSE emissions are available for 2015 and not 2019.  
> **username_1**: That's a separate question, you should post that as a new question.  An emissions modeling platform often uses information from various years depending on availability.  
> **username_0**: Thanks for the advice. I have also asked it as an independent question now.  

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## 1 answers

### Answer by username_2 on 2022-01-15. Score: 1 | Accepted answer

Generally, spin up is necessary. To give context, look at how the model initializes. Does that look anything like a real chemical field? If you don’t have the eye for such things, examine the RMSE or other error metrics and compare them to other studies. Odds are, probably not. So you have to supply the model with emissions data and give a long enough period for it to seem at least plausible.

When I was using WRF-Chem to simulate $\ce{O3}$, I used a couple days for the emission of $\ce{NO\_x}$ to be somewhat representative.

> **Comments:**
> **username_0**: I am new to running the WRF-Chem model, so this question maybe a little elementary. Therefore, I wanted to ask that to perform an year-long simulation of certain chemical species for 2019, would I have to provide the emissions for 2019 or for example, 2015 would suffice. I am assuming that the WRF-Chem model will be able to interpolate the emissions to 2019. The reason I am asking this question is because EDGAR/ECLIPSE emissions are available for 2015 and not 2019.  

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