We have saved CAM-chem simulation output that is intended to be used as boundary conditions for regional modeling. We used CAM-chem at 0.9x1.25 horizontal resolution simulation with 56 vertical levels. Meteorology is driven by specified dynamics, by nudging with 50h relaxation (1%) to MERRA2 reanalysis. Data is saved as instantaneous fields every 6 hours. See a list of saved species. Chemistry is the MOZART-T1 mechanism, described in Emmons et al. (2019). You can find a description of all simulated species online. We use the MAM4-VBS scheme to model aerosols. Files are collected as daily information (4 time-slices per file). Anthropogenic emissions are from CMIP6, CMIP6 2014 anthropogenic emissions are repeated for dates past 2014 to 2016. Anthropogenic and "other" emissions are changed to SSP5-85 for 2017 onwards. Biogenic emissions are from online MEGAN2.1, fire emissions are from QFED CO2 x FINN emission ratios (from 2015), with emission ratios updated from 2017 onwards. Note that fire emitted DMS 2001-2015 is from CMIP6, in 2016 from GFAS and 2017 onwards from QFED. SST in 2019 are repeated from 2018.

*** NOTE: This version of output has incorrect HCN and O3S, please do not use these species ***

Get the data

1. Subset from dates within the time period January 1, 2001 to June 30, 2019

A small subset of the boundary conditions are available via rapid access from the ACOM server:

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

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:

2. All available dates January 1, 2001 to June 30, 2019

To access any of the complete dataset of shared files between January 2001 and December 2018 you will need a Globus account, which requires a Google account. Get Globus access here.

Once you can log into Globus, the boundary conditions are stored here:

January 2001 to June 2017:

January 2017 to December 2018:

Files can be transferred to another location using the Globus system. To set up a transfer point see the relevant page:


Note: direct download option from this site is in beta testing phase and should be available in the future.


To cite the data directly, please use:

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 et al., The Chemistry Mechanism in the Community Earth System Model version 2 (CESM2), JAMES, submitted August, 2019.

Other simulations

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

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: