How to change planetary properties?

[danielkoll]

Is there an easy way to change physical constants, say, if I wanted to run climlab across a range of different surface gravities or atmospheric MMWs? The only way I know of doing this right now would be to make a hard copy of the climlab library, modifying the constants in the copy, then importing both library versions into python. This becomes impractical once I'm thinking about dozens of different parameter values.

**Sub-issues that only matter for non-grey radiation:

• CAM3 currently seems to import its constants from 'climlab/radiation/cam3/src/shr_const_mod.F90', which are different than those set in 'climlab/utils/constants.py'.
• RRTMG appears even more hard-wired, e.g., surface gravity is a fixed value set in 'rrtmg_lw_init.f90'.

To deal with this one would presumably have to modify the fortran structure so CAM3/RRTM get their physical constants as inputs?

[brian-rose]

Short answer is no, there is no easy way to do this. And there should be.

Also I think you raise an important point about possible inconsistencies in physical constants.

I think we'll put this on the list of things to prioritize in the imminent major re-write of climlab internals. Along the lines of #119, the user should be able to pass physical constants as optional keyword arguments to each process.

[brian-rose]

See PR #123. Proof-of-concept for one way to handle this.