[Discussion] Run-time/compile-time switches

[jimmielin]

Right now there are some configurable options for the behavior of the GEOS-Chem within CESM2 model that are scattered about in code. I'll document them here as I find out more about them.

C-Preprocessor constants

• MODAL_AERO and MODAL_AERO_4MODE. I think CESM-GC won't run without aerosols so I don't know why #ifdef for these are still included in chemistry.F90. Perhaps for compile of compsets without MAM4 and not with chemistry?

In chemistry.F90

• debug - controls debug output, together with masterproc. Set to .true. now. I recommend possibly merging this with the option for debug output in the GEOS-Chem config yml.
• ghg_chem - "use ghg chem package" ?? unknown use. Set by namelist.

In GEOS-Chem Input_Opt

• Input_Opt%onlineAlbedo - true to use CLM albedo for photolysis, false to use monthly-mean albedo for HEMCO. Default/recommendation is .true.
• Input_Opt%applyQtend - true to apply tendencies of water vapor (H2O) tracer to specific humidity. Default is .false. - recommendation is unknown.
• Input_Opt%correctConvUTLS - true to apply photolytic correction for convective scavenging of soluble tracers. Default/recommendation is .true.. I implemented this and know that it is necessary to be in Input_Opt as it interfaces with GEOS-Chem source code.