Use MEGAN generated biogenic emissions in CMAQ

Hi all,

I’m asking here how to use MEGAN biogenic emissions in CMAQ. I know that EPA has used before (see https://www3.epa.gov/ttnchie1/conference/ei18/session3/pouliot.pdf). But they didn’t mention how they used MEGAN in the model. So I wonder how people deal with MEGAN emissions. From my understanding, I would combine MEGAN emissions into the surface emission file and set CTM_BIOGEMIS to N. If anyone has worked with MEGAN, could you share your thoughts? I’m looking for some better way to apply MEGAN in CMAQ.

Thanks,
Yusheng

Hi,

Yes, you would merge the MEGAN emissions with the rest of your ground-level 2D emissions. You need to make sure you don’t have the BEIS inline biogenic option turned on in CMAQ when you do the CMAQ run so you don’t double count biogenic
emissions.

Alison

Hi,
You need to run MEGAN (the latest version is MEGAN v3) stand alone to generate biogenic emissions separately, and then as Alison said merge the MEGAN outputs with other surface emissions using SMOKE. Make sure to turn off CTM_BIOGENIS when you get biogenic emissions in this way.

Thanks.
Fliu

Dear @RockeyZ,

Could you tell how did you merge your MEGAN files?
If you can share with me more details about the steps to do it, I would really appreciate it.

Thank you!
Thayná

Hi Thayná,
I didn’t find any easy-to-use tools to merge the files so I wrote a ncl script to manually add each species into existing surface emission file. To do this, I think you may want both MEGAN and surface emission files to have the exactly same dimensions. Noting that when I was merging my MEGAN emissions, I found that the species names didn’t match exactly the species names in the surface emission file so I had to deal with those variables separately. For example, I’m using saprc07 chemical mechanism in CMAQ. I got ISOP in the surface emission file, and ISOPRENE in the MEGAN file. These two names are actually the same species. Another example would be that I have SESQ in the surface emission file, but BCARL, AHUMUL and SSQT in the MEGAN file, which I believe these three species are also SESQ species.
Hope this helps you.
Best,
Yusheng