<p>I have a WRF-chem output with NO<sub>2</sub> mixing ratio for 37 levels, for my analysis I need to convert it into into column density. How do I do that?</p>

CC BY-SA 4.0
2021-11-11T04:56:57.863Z
There are post process calculators that can do this for you easily.  However, if you are planning to compare to satellite retrievals, you are supposed to use the averaging kernels from the satellite instrument algorithm.  Calculating the column density with the satellite averaging kernels creates a large computational burden and requires many QA/QC steps for the satellite data.  So, the answer to your question really depends on your application.
f.thorpe
CC BY-SA 4.0
2021-11-11T05:28:44.537Z
i am trying to convert the mixing ratios into column density so that i can use it as an a priori in VCD data retrievel in TROPOMI instead of the TM5 profile
Sreeraj Ramesh
CC BY-SA 4.0
2021-11-11T05:31:44.687Z
also is it possible to get the WRF-Chem output in the form of column density rather than in the form of mixing ratios?
Sreeraj Ramesh
CC BY-SA 4.0
2021-11-11T16:04:26.123Z
the a priori for TROPOMI should be a profile... not a VCD, right?  I've never heard of an a priori VCD...
f.thorpe
CC BY-SA 4.0
2021-11-11T16:18:12.650Z
Sorry I'm not a WRF-CHEM user, CMAQ has a program called PHOTDIAG that does it and a models-3 program called VERTINTEGRAL can do it.  Though, there is a nice explanation of the simple mathematics here: https://forum.wrfforum.com/viewtopic.php?f=41&t=5552#p19541
f.thorpe
<meteorology><atmosphere><atmosphere-modelling><atmospheric-chemistry>
How to convert $\ce{NO2}$ mixing ratio (ppmv) into $\ce{NO2}$ column density(moles/m2)?
Sreeraj Ramesh
# How to convert $\ce{NO2}$ mixing ratio (ppmv) into $\ce{NO2}$ column density(moles/m2)?

(Asked by: username_0 on 2021-11-11)

I have a WRF-chem output with NO2 mixing ratio for 37 levels, for my analysis I need to convert it into into column density. How do I do that?

**Tags:** meteorology, atmosphere, atmosphere-modelling, atmospheric-chemistry

> **Comments:**
> **username_1**: There are post process calculators that can do this for you easily.  However, if you are planning to compare to satellite retrievals, you are supposed to use the averaging kernels from the satellite instrument algorithm.  Calculating the column density with the satellite averaging kernels creates a large computational burden and requires many QA/QC steps for the satellite data.  So, the answer to your question really depends on your application.  
> **username_0**: i am trying to convert the mixing ratios into column density so that i can use it as an a priori in VCD data retrievel in TROPOMI instead of the TM5 profile  
> **username_0**: also is it possible to get the WRF-Chem output in the form of column density rather than in the form of mixing ratios?  
> **username_1**: the a priori for TROPOMI should be a profile... not a VCD, right?  I've never heard of an a priori VCD...  
> **username_1**: Sorry I'm not a WRF-CHEM user, CMAQ has a program called PHOTDIAG that does it and a models-3 program called VERTINTEGRAL can do it.  Though, there is a nice explanation of the simple mathematics here: https://forum.wrfforum.com/viewtopic.php?f=41&t=5552#p19541  

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## 0 answers

