#554: Improve set up of fields on coarse grid in LFRic

[mcdalvi]

Are there any linked Issues or Pull Requests?

No response

Brief description

Currently, LFRic atmosphere contains a few fields (aerosols, nudging after #474) defined on a coarse mesh i.e. different mesh to 'dynamics'.
The setup and reation of these fields however, requires adding/ using bespoke arguments to field creation functions, eg. in create_physics_prognostics

call processor%apply(make_spec('ait_sol_om', main%aerosol, Wtheta, **coarse=coarse_rad_aerosol,  &
        coarse_mesh_name=mesh_name**, adv_coll=if_adv(advection_flag, adv%last_con),                 &
        ckp=checkpoint_flag))

If there are another set of physics fields that move to a coarse mesh this may add further complexity to the definitions.

There is hence a need to design a robust and flexible way to handle the coarse mesh fields.

Further details of the issue.

No response