We have saved CAM-chem simulation output that is intended to be used as boundary conditions for regional modeling. We used CAM-chem in the finite volume dynamical core, at 1 degree global horizontal resolution with 32 vertical levels. Meteorology is driven by specified dynamics, by nudging with 12h relaxation (10%) to MERRA2 reanalysis. Data is saved as instantaneous fields every 6 hours. See a list of saved species. Chemistry is calculated using the MOZART-T1 mechanism, described in Emmons et al. (2020). We use the MAM4-VBS scheme to model aerosols. Anthropogenic emissions are from CAMS-GLOB-ANTv5.1. Biogenic emissions are from online MEGAN2.1 modeled interactively via CLM. Fire emissions are from QFED CO2 x FINN emission ratios. Data Format: netCDF

  • File size: 1.79 GB per day (4 x 6-hour instantaneous time slices per day)

  • Data coverage: January 1, 2001 to December 30, 2020

*** We have yet to simulate past 2020, and envision this could take some time as we finalize input datasets ***

For more recent dates, you could consider using the WACCM forecast for boundary conditions, which is available from January 1, 2020 to 10 days from now:

Get the data

1. Subset from dates within the time period January 1, 2001 to December 31, 2022

Regional and temporal subsetting can be found at: Note there is a limit to download data in chunks of 32 days per download.

2. Global files

Direct data download of global files is also available from the NCAR Research Data Archive; registration is required.


When using the data, please cite:

Tilmes, S., Emmons, L.K., Buchholz, R.R. & The CESM2 Development Team, (2022). CESM2.2/CAM-chem Output for Boundary Conditions. UCAR/NCAR - Atmospheric Chemistry Observations and Modeling Laboratory. Subset used XXX, Accessed* dd mmm yyyy, DOI:

Please fill in the "subset used" with region and/or date of the subset you used (e.g. Lat: -10 to 10, Lon: 100 to 150, September 2015 - February 2016).

*Please fill in the "Accessed" date with the day, month, and year that you last accessed the data (e.g. - 5 Aug 2011).

Using the boundary conditions with WRF-Chem

The CAM-chem chemistry and aerosols for this run are identical to the WACCM forecasts. Mapping CAM-chem output to WRF-Chem chemistry schemes can be found in:

which is linked from this page:

Other simulations

Old Boundary Conditions: CAM-chem simulations with CESM2.1 covering 2001 to 2020 can be found here: CESM2.1:CAM-chem as Boundary Conditions The dataset is no longer maintained.

Directions to access other experimental output can be found here: Benchmarks and Production

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