Retire CH4, CO2, tagCO simulations in favor of carbon simulation

[msulprizio]

Your name

Melissa Sulprizio

Your affiliation

Harvard

Provide a clear and concise overview of the new feature requested.

The carbon simulation now combines CH4, CO2, CO, and OCS into a single simulation that utilizes KPP as the chemical solver instead of independent chemistry routines within global_ch4_mod.F90, co2_mod.F90, and tagged_co_mod.F90. It can also be run in single-tracer mode. The single-tracer CH4 carbon simulation has been validated by @msulprizio and the single-tracer CO2 simulation is being validated by @hannahnesser. So far the single-tracer simulations are nearly identical to the existing CH4 and CO2 simulations.

We prose retiring the CH4, CO2, and tagCO simulation options and recommend using the carbon simulation in GCClassic and GCHP instead. This was approved by the Carbon Cycle Working Group at IGC11.

Reference(s)

None

Will you be implementing this feature yourself?

Yes

Additional information

Tagging also @kbowman77 @yantosca @lizziel

[msulprizio]

See also geoschem/GCHP#430

[msulprizio]

I removed the 14.5.0 milestone for now since it's not clear we will be able to retire these simulations for that version with the freeze date planned for the end of this month.

There are still some lingering issues that @lizziel discovered in testing the carbon simulation in joint-species mode and single-tracer mode in both GCClassic and GCHP. Mainly there are (1) differences in CO2 in the joint vs single-tracer simulations in GCClassic and (2) issues with the restart file in GCHP.

[yantosca]

Also see #2463