Enable prescribed CO2

[LenkaNovak]

In AMIP II, CO2 is prescribed at 348 ppmv (see requirements), but we want to demonstrate time varying CO2. Several options exist, but for now ClimaAtmos interface allows only one global value. Since CO2 is generally well mixed, we implement temporally varying global values (represented by the Mauna Loa record). This follows some CMIP experiments. At the next stage will allow CO2 to be a function latitude or use gridded files, as is done in the latest CMIP models.

components

• ensure we can change radiation CO2 externally from ClimaAtmos
• read global mean CO2 from file: https://gml.noaa.gov/webdata/ccgg/trends/co2/co2_mm_mlo.txt
  • since general file reads will be dealt with in ClimaUtilities soon, here the CO2 prescription was implemented with minimal disruption to our src code. This meant:
    • converting the .txt file into a netcdf file of the same format as the SST and SIC files
    • saving the file as a new artifact on Box
    • enabled the specification in the driver

In ClimaUtilities, we want to deal with this more generally @juliasloan25 . We will need to

• agree on accepted formats for forcing / boundary condition files
  • formats of files with 3d and 2d fields (presumably netcdf with time, z, lat, lon makes most sense)
  • formats of files with 1d fields (CSV with standard headings, TBD)
  • time variable (hours since epoch? e.g. 1800-01-01 00:00:00)
• come up with a better interface that reduces code in the driver

QA

• demonstrate change in Buildkite
  • with co2 https://buildkite.com/clima/climacoupler-ci/builds/1878
  • w/o co2 https://buildkite.com/clima/climacoupler-ci/builds/1873
• come but not huge increase in walltime (1h42 vs 1h30 for 30 days)

#Potential next steps

• add other gases and latitudinal dependence: https://gmd.copernicus.org/articles/10/2057/2017/
  • this requires enabling atmos_sim.integrator.p.radiation_model.volume_mixing_ratio_co2 to be a 2d field
• add gridded CO2 data: https://www.nature.com/articles/s41597-022-01196-7
  • this requires enabling atmos_sim.integrator.p.radiation_model.volume_mixing_ratio_co2 to be a 2d field