Dear Julio,

One important file related to VOCs is the biogenic emissions. Plants are know be significant sources of VOCs. Sometimes, they can be the main source of VOC! Therefore, I suggest you to include in your simulation an emission inventory for this source. You can use the MEGAN model to generate the files.

Also related to VOCs, you can investigate the Ozone (O3) formation. There are a relationship between NOx and VOC in O3 formation. Changing the emissions, an impact in ozone concentrations are expected.

Dear William,

Yes, I think properly including MEGAN is a way to refine VOCs emissions. I agree with you that it would improve the VOCs representation.

And yes, we were expecting a change in ozone in the sensitivity scenario due to the decrease in VOCs and NOx we used as input to the model. However, none of the above variables in the emission files show a decrease in VOCs emission. So I am wondering if we did something wrong when assigning emissions in the sensitivity scenario.

Thanks for your interest and reply.

Best,

Hey guys,

First:

"We are running WRF/Chem 4.5.1 with RADM2."

Good

"In the wrfchemi files, I am looking at the E_NH3, BIGALK and E_C3H6."

The registry.chem states that for RAMD2, the emis_opt species are:

"E_ALD" "E_CO" "E_CSL" "E_ETH" "E_HC3" "E_HC5" "E_HC8"

"E_HCHO" "E_ISO" "E_KET" "E_NH3" "E_NO" "E_OL2" "E_OLI"

"E_OLT" "E_ORA2" "E_SO2" "E_TOL" "E_XYL"

In R you may install eixport (https://atmoschem.github.io/eixport/index.html) and do

R>remotes::install_github("atmoschem/eixport")

R>library(eixport)

R>data(emis_opt)

R>emis_opt$eradm

However, the emissions schemes that include "BIGALK" are:

• mozem
• mozcem
• mozmem
• mozc_t1_em

R>names(emis_opt)[grep("BIGALK", emis_opt)]

"in the latter, there were decreases in total pollutants emissions, including VOCs... However, I don't see much change in VOCs between the two simulations, neither in the emission files nor in the output files."

It is important to check the wrfchemi files before running WRF CHEM. You can do that with a summary of the variables. For instance:

R>wrf_summary("wrfchemi_d02")

R>wrf_summary("wrfout")

I agree with Willian Andreão that BVOC are important, but according to my understanding, there is an option to estimate BVOC online, the default. Therefore, if your focus is not BVOC, I would just be sure that MEGAN is estimated online with WRF CHEM and move forward.

Finally, check your chem_opt and emiss_opt in your namelist.input. You may be including emissions, such as BIGALK, that would not be read.

Thank you so much for lending your expertise, Sergio Ibarra-Espinosa . I will definitely take a careful look at your suggestions, as the VOC decrease in an interesting part of the work I am doing now and I don't want to miss it.

R can be very useful...

Cheers and best regards my friend.

Hi Julio,

If you are changing both anthropogenic and biogenic VOC emissions and are not obtaining different concentration, the problem could be related to the boundary condition. Maybe expanding the domain may diminish this influence. Or using different database to provide this boundary concentrations.

If you are not changing the biogenic VOC emissions, and the final concentrations is similar, this mean that this emission type might the main source of VOC. Therefore, the chances in anthropogenic emission do not cause any effect.

You can summarize each VOC species emission (_NH3, BIGALK and E_C3H6 ) by sectors (anthropogenic, biogenic, fires, etc.) to see the most representative sector.

For curiosity, the O3 concentration also changed in the second scenario?

I really appreciate your insights William. We will definitely try different configurations and check the changes.

Actually, the magnitude of of biogenic VOCs compared to anthropogenic VOCs in my region is still a bit unknown, we assume anthropogenic is higher due to the huge vehicular emissions, but as far as I know, we still lack on comparing studies between both VOC sources (as far as I know). Actually, that would make a very interesting research topic on itself.

On average, the O3 concentrations increased in the second scenario. But we also decrease NOx emissions, so it may be related to just that. We were hoping to see the impact on ozone by decreasing NOx AND VOCs, since my region is NOx-saturated, but since we are not sure if the VOCs emissions are right, we cannot conclude anything on the O3 concentrations yet.

Thanks a lot for the interesting discussions!