Discuss unification of above-model-top parameterizations

### Issue Type

Infrastructure Update

### Issue Description

Would it be possible to come up with a unified way of parameterizing stuff that exists above the model top? Some packages (radiation, photolysis, others(?)) sometimes need to know what exists above the model top, and it may be preferable to have CAM-SIMA provide this, rather than each package implementing their own parameterizations if possible.

### Will this change answers?

I Don't Know

### Will you be implementing this yourself?

Any Software Engineer can do this