Ammonia column density in CMAQv5.3.2

I am working on comparing the ammonia vertical column with satellites such as IASI and CrIS. However, it looks like the ammonia vertical column density is not a variable in CCTM_PHOTDIAG1_ outfile for the CMAQv5.3.2 (it only has NO2, O3, SO2). May I ask how could I get the ammonia column density from CMAQ? Shall I use the m3tools?

This may not be exactly what you want, but the M3Tools program vertintegral would probably be a good starting point (You’d need to derive ammonia from CMAQ concentrations).

Yes, this is also what I am thinking about. By using this to derive the total vertical ammonia concentration than convert the unit to molec/cm2. Am I right?

If I understand what you want correctly…

Christian – does that sound right?

I haven’t used vertintegral myself, but looking at the documentation and the fact that it reads layer heights and densities from METCRO3D and 3D concentrations from CONC, this seems consistent with how column densities for selected gases are calculated in the CMAQ PHOTDIAG code. I guess for the conversion to molec/cm2 you have to look at the vertintegral code and work through the units in the input files to figure out what needs to be done.

Thanks for the clarification. May I ask whether the next version of CMAQ will include the NH3 column density in the CCTM output files?
(Just out of curiosity

I can share that suggestion with the development team.

Please share with the develop team!

you may be able to calculate the ammonia VCD similar to equation 4:
–though the satellite retrieval has a vertical sensitivity that won’t be reflected in a non-weighted integration of model layers. This shouldn’t be a huge deal if the retrieval is most sensitive near the surface, but even if so it’s worth noting that it’s not an exact apples-to-apples comparison.

Thanks a lot for mentioning this! I will check it out.
Really appreciated!