Regridding between 12km and 36km CMAQ-ready emissions

I was curious what issues I need to address or pay attention to when I am regridding a fine 12km CMAQ-ready NEI emissions files to a coarser 36km grid, and similarly if there any issues I should be careful about when regridding a coarse 36km CMAQ-ready NEI emissions files to a finer 12km grid? My intention in both cases is to use the regridded CMAQ-ready emissions for input into CMAQ simulations. Is it sufficient to check that emissions rate is equal in the original and the regridded files?

The issue is that emissions values are not in an interpolatable MKS unit but instead are in non_MKS “mass per grid cell per unit time” units. You must be careful to multiply the aggregated result by the ratio of the grid-cell areas (which for re-aggregating 12KM cells to 36KM cells is 9).

So, is this question your own case or a case you downloaded from a repository?

At this point, I am trying to use the repository CMAQ emissions input but I am assuming there are certain sectors that are meteorology dependent, which means I will have to generate at least those on my own using my meteorology. Anyways, I plan to do both 36km and 12km CMAQ runs, and I was thinking being able to regrid from 12km ready-made emissions to 36km or regridding 36km ready-made emissions to 12km would be quick!

There are already 36km emissions available for certain cases. Which cases are you wanting to model? Typically the 36km domains are larger than the 12km.

I have been able to check and verify that my current WRF (with 36km and 12km nested simulations) domain easily accommodates the 12US2 domain, so the 12US2 emissions should be handy (I am not sure which 36km domain I should use for CMAQ simulations.

When I check the CMAS data warehouse, I saw that the data was grouped into the following:

Under the category 2016fd_db6_16j > 12US2 > cmaq_cb6, I see the following files:
emis_mole (January and July files e.g. emis_mole_all_20160706_12US2_withbeis_2016fd_cb6_16j.ncf.gz)

I’m not sure if above is a complete list of emissions needed for CMAQ, but I was looking to use the full year NEI emissions (2016NEI is probably the most representative of present day emissions). Is a full set (all emission sectors) of one year of 2016NEI data in CMAQv5.3.1-friendly form (CB6 bond, AE7 aerosol module, 12km and 36km domains) ready for the public?

The 2016 beta platform is a bit newer than the 2016fd case and includes 36km emissions inputs, and the 2016v1 platform is even newer than that. These are available here:

Make sure you have the right modeling platform selected in the #1 selection box if you want to download emissions.

Thanks for the link - I signed up and made the data request, and I am told to wait until they contact. Is the same data also available at or are the two different in some respects?

Only the SMOKE inputs are on the newftp site. The IWDW has the SMOKE outputs as well.

Aren’t the 36km and 12km files available for the 2016 platform here:
List of files:

Yes, they are also there. Sorry, for some reason I only the 12km were there.

That is a newer version than the user is using.

Could you show the explicit path on Google Drive for both the 12km and 36km resolutions (e.g. CMAS Data Warehouse > SMOKE > Output > 2016fd_db6_16j > 12US2 > cmaq_cb6) as Google Drive links are not self explanatory like ftp links?

Here is the path for the 2016 Platform Data

CMAS Data Warehouse > SMOKE > Output > 2016Platform > 2016fh_16j
The data is contained within the premerged folder under the above directory.
There is a spreadsheet at that same level that shows what data is available.

Thanks a lot, I was able to download both 36US3 and 12US1 emissions files from the Google Drive storage of CMAS Warehouse. I was a little unsure about few things though:

  1. Two broad categories of files are there for each grid: emis_mole files that I could see maps of on ‘ncview’ and inline files which could not be viewed on ‘ncview’ and probably need further processing; what are the two categories for and how should I feed them in CMAQ?
  2. There is one file for 12US2 grid (others are all for 12US1 grid), namely for the 12US2_ptagfire3D sector and I was not sure what to do with it.
  3. I have my own WRF meteorology, so I am assuming I will need to process some meteorology-dependent sectors on my own in the 2016 platform before input to CMAQ- which sectors (beis? dust?) are meteorology dependent in the 2016platform?
  4. Are the emission files in EPA ftp server coded such that 2016v1platform files are labelled ‘2016fh’, 2016betaplatform files are ‘2016ff’ and then there are ‘2016fd’ files which are like first versions of 2016NEI files?

Thanks in advance!

Hi – a few responses:

The inln files are for point sources that have plume rise, while the emis_mole files are 2d emissions files. CMAQ should accept both types of emissions files. You’ll need to look at the documentation to determine how to provide them.

3D fire files are precursors for CAMx – if you are running CMAQ you probably don’t need this. Do you also see a 12US1 ptagfire file?

If you want to reprocess some met-dependent sectors, you can. You should review one of our emissions modeling TSDs to understand which sectors are met dependent. This is the only full TSD for 2016 platform
– otherwise details for each sector are on the IWDW. For example, BEIS can be reprocessed, or you can instead tell CMAQ to compute biogenic emissions in line, in which
case you would not feed them in as part of emis 2D files. Dust emissions are adjusted down according to meteorology. Residential wood and ag emissions are temporally allocated according to meteorology, but you don’t necessarily need to reprocess them – you
could still use them as is. Onroad emissions are computed based on temperatures, but I wouldn’t recommend recomputing those unless you really have to.

The various 2016 versions are here:
The 2016fh emissions are the most recent. I’m not sure why you would want to use 2016fd (alpha) instead of 2016fh. The data for 2016fh are much more updated
with input from states and updated methods.

Thanks a lot - I think I have enough information to go ahead and prepare for my CMAQ simulations now. I will keep this thread ‘open’ for a while just in case I have some questions relating to emissions.

Hi, I am cropping some grid cells off the edges of the 36US3 emissions files from the 2016 v1 Platform to suit my smaller meteorology domain. I can subset the gridded 2D emissions files easily, but I am not sure how to ‘window’ into the non-gridded inline emissions files (and their accompanying stack_groups files).

Hi, do you need to use 36km files? There are 12km files available as well – just making sure you knew that.

For the inline emissions, the models don’t need for you to window them down to run a smaller grid.

Thanks - I am aware of the 12US1 emissions files as you pointed to the CMAS Warehouse - I am starting with the 36US3 emissions first.

As I enter the emissions file locations into CMAQ run code, I am seeing that I have to merge all gridded emissions files into one, except the inline biogenic emissions, inline windblown dust and gridded residential emissions ‘rwc’. I have two questions here:

  1. What is the easiest tool to merge all CMASwarehouse gridded emissions files into one - some specific I/O API commands or the SMOKE program itself?
  2. Why is ‘rwc’ sector separately read in CMAQ run code even though it is represented by gridded 2D emissions like many other sectors?