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Inverse of air density (alt) from wrf-chem output

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New member
Hi All,
Is there any way to obtain variable alt (inverse of density of air) from output of WRF-Chem v3.9 model using NCAR Command Language (NCL)?
Note: variable 'alt' is used in chemistry modules of WRF-Chem to convert mixing ratio (in kg/kg-air) to concentration (ug/m3).

I'm sorry, but I don't really understand your questions. Are you just trying to extract the variable from the output, or calculate it?
Hello, has anyone found out how to do this? I would like to be able to read the inverse of air density from the model, NOT calculate it (although if this is not possible, I will have to do that). I would like to see what the exact value that the model uses is.
I think the solution to this issue is to add an "h" to the registry Registry.EM.COMMON

Specifically, change:

"state real alt ikj dyn_em 1 - r "alt" "inverse density" "m3 kg-1""


"state real alt ikj dyn_em 1 - rh "alt" "inverse density" "m3 kg-1""

Then you need to rebuild your instance of WRF and alt should be included in the wrfout files

Alternatively, if you don't want to recompile you can add it to the wrfout as detailed in the "o. Run-Time IO" section in this document.