which means that it cannot get colder that the mountains already are
Absolutely it can. That’s the adiabatic expansion: air gets colder precisely by expanding against other air. No mountain needed.
As to solar absorbtion, the mountain is a good point: the sun is actually incredibly strong on mountains, because less air above is absorbing light, meaning, I think, you’ve actually got more intense surface heating at the top of a mountain, unless there’s snow to reflect the heat.
Absolutely it can. That’s the adiabatic expansion: air gets colder precisely by expanding against other air. No mountain needed.
As to solar absorbtion, the mountain is a good point: the sun is actually incredibly strong on mountains, because less air above is absorbing light, meaning, I think, you’ve actually got more intense surface heating at the top of a mountain, unless there’s snow to reflect the heat.