Is it reasonable to scale and subtract onroad_ca_adj from emis_mole_all?

I’m teaching an undergraduate research course (CURE type course) involving atmospheric chemistry. One project is looking at the effect of mobile emissions on air quality in California. We will look into various mobile sources eventually, but for now I’m just focusing on running CMAQ with emissions scaling for all mobile sources. Since this is for an Undergraduate level class I’m hoping to get away with using CMAQ ready emissions and meterology files, which I’ve obtained from the Google Drive (thanks so much for having these!).

My thoughts on the easiest way to start were to use the merged gridded emissions data and subtract premerged onroad_ca_adj using the DESID emissions scaling. For example:

Base case:
‘EVERYWHERE’, ‘ONROAD_CA’ ,‘All’ ,‘All’ ,‘All’ ,0. ,‘UNIT’,‘m’,!Base case.
Extreme case: no onroad emisisons
‘EVERYWHERE’, ‘ONROAD_CA’ ,‘All’ ,‘All’ ,‘All’ ,-1. ,‘UNIT’,‘m’,!Subtract out all onroad emissions.

I’m using these gridded emissions files from the Google Drive (along with STK_EMIS files)
emis_mole_all_{YYYYMMDD}_12US1_nobeis_2016ff_16j_norwc.ncf emis_mole_onroad_ca_adj_{YYYYMMDD}_12US1_cmaq_cb6_2016ff_16j.ncf

I just wanted to check if this was reasonable to subtract these two emissions sets like this.


Hi Mark,

We’re so glad CMAQ is going to be useful for your course. You are exactly correct. These rules that you are passing through DESID should give unperturbed emissions for your base case and zero out onroad emissions for your ‘Extreme Case’. Perhaps you have tested them already – if you have seen anything strange in the results, please let me know and I can help track down the cause.

Sorry for the delay, and best wishes!

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Hi Ben,

Thanks, that’s good to hear. I have one more question:

Is it possible to use SMOKE data produced for the 12US1 grid if I’m running simulations on the smaller 12US2 grid? CMAQ doesn’t give any errors, but I thought I’d ask.