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  • CESM2.1:CAM-chem as Boundary Conditions

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

*** Boundary conditions usually lag by approximately 6 months due to input file availability. Currently with COVID-19 the lag is longer. ***

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



Buchholz, R. R., Emmons, L. K., Tilmes, S., & The CESM2 Development Team. , (2019). CESM2.1/CAM-chem Instantaneous Output for Boundary Conditions. UCAR/NCAR - Atmospheric Chemistry Observations and Modeling Laboratory. Subset used XXX, Accessed* dd mmm yyyy,

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).

We suggest to also cite the following paper that discusses the new configuration of CESM2/CAM-chem and assesses chemical species, including using output from this boundary condition simulation.


Emmons, L. K., Schwantes, R. H., Orlando, J. J., Tyndall, G., Kinnison, D., Lamarque, J.‐F., et al., (2020). The Chemistry Mechanism in the Community Earth System Model version 2 (CESM2), JAMES, submitted August, 2019.. Journal of Advances in Modeling Earth Systems, 12, e2019MS001882,

Other simulations

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