Why does the atmosphere get colder with elevation?

[D H]

With a solar constant of about 1360 w/m2 and an albedo of 30%, the square meter directly under the sun has an equilibrium temperature of 360K when using Stefan Boltzmann. This is comparable with the max temp of the moon.

If the ambient temperature is -18°C, 255K and the surface boundary layer of the atmosphere under the zenith is heated via conduction approaching 360K, what would stop the convection?

You're assuming a lot here. You are assuming a significant heat transfer rate from the surface to the surface boundary layer, and you assuming an ambient temperature of -18°C.

I thought I had read articles on a greenhouse gas free atmosphere, but the closest I can find in the scientific literature are articles snowball Earth. Those studies however still had CO₂ and other greenhouse gases in the atmosphere.

We're both speculating, so the best thing to do is to stop with this particular line of discussion.

@DH
I'm not talking black bodies. I talking about every real thing. Since when did gases not absorb and emit EM? I never implied broad band behaviour

Oxygen and nitrogen don't, or at least not very much. Those simple diatomic gases don't absorb much in the IR, so they don't emit in that band. Absorption and emissivity go hand-in-hand. That O₂ and N₂ are not thermally active is key to remote sensing. We wouldn't be able to use those satellite-based water vapor channels to "see" water vapor in the atmosphere if oxygen and nitrogen absorbed and emitted thermal radiation.

Addendum
An even better example are the noble gases. These gases are even more immune from thermal radiation than are the diatomic gases. This is why expensive double pane windows are filled with argon, and even more expensive ones are filled with krypton. Cheap ones are filled with nitrogen, and even cheaper ones are filled with dry air.

 

[Andre]

We're both speculating, so the best thing to do is to stop with this particular line of discussion.

Fair enough. I'm intending send you a pm tomorrow.