pairing E3SMv3 with offline RRTMG double calls

[jazweifel]

Hi all,

I'm working on some E3SMv3 simulations and am hoping to configure a setup so that can I perform offline RRTMG radiation diagnostics to estimate aerosol direct and indirect cloud forcing. This would be in line with approaches described by Steve Ghan in 2013 Technical Note

The group I'm in is interested in applying the double-call methodology on varying atmospheric profiles we describe as: base (unchanged), clean (aerosols removed), clear (clouds removed) and clean_clear (aerosols and clouds removed) and calculate net shortwave fluxes at TOA. We've done this previously in CESM2 using paired radiation calls, and are now hoping to do something analogous within E3SM.

At this point we are wondering what the best steps would be to:

Enable offline RRTMG double-call functionality and output the necessary flux diagnostics to compute aerosol direct forcing, aerosol-cloud indirect forcing, and surface-albedo forcing.

I'm also curious whether there are relevant E3SM namelist options or CAM radiation diagnostics packages that need to be activated to facilitate this. If anyone has guidance on offline RRTMG usage in E3SMv3 or examples of successful aerosol forcing diagnostics in this framework, I would really appreciate the help.

Thanks!

Jack