CMAQ Nested Simulations


I am wondering how should I approach CMAQ nested simulations in terms of preparing fixed files?

I may clarify that I already know about:
1- Gridded emission should be disaggregated by conserving the mass (e.g., using M3CPLE with correct setting for SCALEFAC option)
2- Point source emission work with no problem
3- Meteorology will be produced using MCIP with the proper domain definition
4- IC/BC will be produced using icon/bcon programs from the main domain

I would also appreciate any additional suggestions and guidance.


In theory, you could use the same regridding approach you plan to use for gridded emissions to regrid these other files.

However, just as it would be better to regenerate gridded emissions from the underlying inventories and gridding surrogates for your nested domain by running SMOKE so as to better capture the spatial texture of features like roadways, population distribution, etc., it would also be better to do so for the files you listed. For BEIS_NORM_EMIS, this would mean running SMOKE’s normbeis program for your intended domain using higher-resolution BELD input data which should be available, though you’d probably have to ask the SMOKE community for help. To generate a higher resolution OCEAN file, follow this tutorial. To generate higher-resolution input files for the NH3 bi-directional option from scratch, you’d have to run FEST-C.

In the end, you’ll have to think through what you want to get out of the higher resolution nested simulations. It seems you initially considered interpolating meteorology, and here you mention interpolating emissions. What are the features that you did not consider represented at a fine enough resolution in your current domain that make you consider running a higher resolution nested domain? These are the features you will want to prepare “from scratch” for your finer resolution domain, rather than just regridding from your coarser domain.


Thank you for your response!
Very good question. So let me tell you more about specifically the goal that I am looking to:
The meteorology that I am using comes from GFS processed by NACC (GitHub - noaa-oar-arl/NACC: NOAA-EPA Atmosphere-Chemistry Coupler, based and build on MCIP). We currently have the NACC processed outputs and the main GFS files are missing, so this is why I was trying to find a workaround somehow have it at 3km in my domain, and since we want to keep GFS physics intact, we are not currently aiming to run WRF on top as a dynamic downscaling option.
We currently have gridded emission files at 1km resolution that I’m interpolating into 3km and 12km resolutions.
The main purpose can be mentioned here, which is checking the sensitivity/improvements over the target domain at the different resolutions while utilizing the 1km emission files.