Split up marbl_mod.F90

[mnlevy1981]

marbl_mod.F90 could likely be refactored into

1. marbl_surface_forcing_mod.F90
2. marbl_interior_forcing_mod.F90
3. marbl_setup_mod.F90 (for configuration and initialization routines)

This would be an aesthetic fix, making the code significantly more readable / navigable. It would likely not have an effect on the interface, so we can decide if we want to go down this path post MARBL 1.0.0.

[mnlevy1981]

Don't want _forcing in the module name

[mnlevy1981]

I have a branch where I split marbl_mod.F90 into marbl_surface_mod.F90, marbl_interior_mod.F90, and marbl_glo_avg_mod.F90. I still need to come up with better names for set_surface_forcing() and set_interior_forcing() -- I was thinking marbl_surface_fluxes_compute() and marbl_interior_tendencies_compute()? marbl_surface_compute_fluxes() and marbl_interior_compute_tendencies() is another option, though I don't really like splitting the phrases "surface fluxes" and "interior tendencies" like that.

Note that marbl_interior_mod.F90 also has marbl_set_global_scalars_interior(), which I could see naming marbl_interior_set_global_scalars() or I can move it into marbl_glo_avg_mod (marbl_glo_avg_set_interior_scalars()?). I haven't done that because the subroutine basically just calls adjust_bury_coeff(), which I think belongs in marbl_interior_mod.F90.

[mnlevy1981]

Now I'm leaning towards marbl_interior_compute_tendencies(). I think that works best with the other subroutines in interacts with -- on the interface, we'll have marbl_interface%compute_tendencies(), and for the carbon isotope tracers we'll have marbl_ciso_compute_tendencies(). Similarly, we can have marbl_surface_compute_fluxes(), marbl_interface%compute_fluxes(), and marbl_ciso_compute_fluxes().

Note that splitting marbl_mod introduces a discrepancy between how we treat the base tracers (split between marbl_surface_mod and marbl_interior_mod) and how we treat the carbon isotopes. Should marbl_ciso_mod be split into marbl_ciso_init_mod, marbl_ciso_surface_mod, and marbl_ciso_interior_mod?

[mnlevy1981]

After talking with @klindsay28 we decided that the verb should go last in all of these routines. So one more round of renaming, such thatmarbl_interface%surface_flux_compute() calls marbl_surface_flux_mod::marbl_surface_flux_compute(), which then calls marbl_ciso_surface_flux_mod::marbl_ciso_surface_flux_compute() (and similar for interior_tendency).

A couple of notes:

1. I will also rename marbl_nhx_surface_emis_mod::marbl_comp_nhx_surface_emis() to marbl_nhx_surface_emis_compute()
2. I'll open a new ticket for cleaning up marbl_co2calc_mod.F90 - I haven't looked closely, but that'll probably turn into marbl_co2_mod.F90 with a lot of marbl_co2_XYZ_compute() subroutines.

[mnlevy1981]

fixed by #308