CONUS 12km ready concentration data for ICON and BCON in a 4km grid

Hello all,

I want to run CMAQ for a 4km resolution around Florida for the entirety of 2022. For that, I need the initial and boundary condition files from the 12CONUS1 domain that was available for any year. (2017 preferable). Can anyone give me links from where I can download the ready aconc file for the 12CONUS1 domain for an entire year to be used as initial and boundary conditions?

Thank you for your help.

Hasibul

Can anyone give me links from where I can download the ready aconc file for the 12CONUS1 domain for an entire year to be used as initial and boundary conditions?

Generally, you would want CONC, not ACONC files for a larger domain to generate initial and boundary conditions for a smaller domain, because CONC files from typical daily simulations contain 25 instantaneous time steps spanning the entire midnight to midnight period for which boundary conditions need to be generated (just like typical MCIP and emission files span the entire midnight to midnight period) while ACONC files (representing hourly average concentrations) contain only 24 time steps. You could string together ACONC-based BCON files, but that’d just require a little bit of extra effort.

Moreover, you need 3D files from the larger domain to generate boundary and initial conditions (which need to span all layers of the smaller domain), and in most applications, users do not configure CMAQ to generate 3D ACONC files.

Finally, the larger domain 3D files you’re looking for also need to contain all mechanism species (or at least all the longer-lived species) used in your smaller domain. To save output space and run times, many applications I know of (including the CMAQ example run scripts) configure their CONC files to just save a small subset of species that may be useful for subsequent analyses and possibly write out just the first layer, unless they have definite plan for subsequent smaller domain simulations. Such CONC files with only a subset of species and/or less than the full set of vertical layers would make them unsuitable to generate initial and boundary conditions for a smaller domain.

For the standard 12CONUS1 domain, a CONC file with all species and all layers would be on the order of 100 GB per day, so an annual set of such files would be on the order of 35 TB. I am not aware of a group that makes such a set available online, even if they generated full 3D CONC files with all species (which many groups do not). However, maybe such sets exist, and if they do, it’d be great for others to share their availability here.

I want to run CMAQ for a 4km resolution around Florida for the entirety of 2022. For that, I need the initial and boundary condition files from the 12CONUS1 domain that was available for any year. (2017 preferable).

Now, while it’s not 12 km data, and while the data doesn’t exist for 2022, the monthly files with daily average CONC files from the 2002 - 2017 108 km H-CMAQ simulations performed for the EQUATES project might be a potential option for you, if you don’t mind the mismatch in years and are o.k. about using concentration fields from a 108 km simulation as inputs to your 4 km simulation. It’s likely not a preferred approach, but depending on your project objectives and resource constraints, it might be an option to consider. For more information on how to obtain and process the data, see this tutorial

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If I am interested in only Layer 1 concentration for both coarse and fine domains, still do I have to write all the layers for ICON and BCON? The coarse domain is CONUS12 so it is storage expensive to write all the layers.

Hasibul

If you want to use coarse domain output to create initial and boundary conditions for your fine domain, then yes, you need to write out all layers for your coarse domain CONC files. Initial and boundary conditions are, by definition, 3D files (unless in the hypothetical scenario where you’re actually running the model for the fine domain as a 2D model with only a single layer, no vertical transport, no clouds, all emissions in that single layer, etc. - which I’m not sure is even feasible with the current setup of CMAQ, and it certainly wouldn’t be realistic), so there’s no realistic way to create initial and boundary conditions from 2D coarse domain output.

Put differently, even if you’re ultimately only interested in analyzing 2D outputs at the surface, these 2D outputs are still affected by 3D atmospheric processes and to represent these processes, the model is set up as a 3D model, requiring 3D initial and boundary conditions.

Given that it is indeed storage intensive to save 3D CONC files with all species from the coarse simulation (which is why such files likely aren’t available online for annual periods as noted in my previous post), one approach might be to write out the full 3D coarse grid CONC file each day, then process it through BCON (and maybe ICON for selected days on which you want to initialize the fien domain), and then delete that 3D CONC file (possibly after saving a subset of species and/or layers you’d like to analyze later), so it’d only take up some space temporarily. Of course you’d want to check that the process works properly and generates usable BCON files before automating such a workflow.

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