Comment on If hot air rises, why is it colder at the top of a mountain?
milicent_bystandr@lemm.ee 2 months agoI believe it’s less about heat dissipation than about adiabatic expansion - where air as it expands does ‘work’ and loses heat.
The heat coming (as far as the air is concerned) mainly from the ground sounds like a good point, but IIRC the temperature at altitude follows the expected curve for adiabatic expansion given the pressure change, so I think that heat-entry-point-effect must be much less significant except close to the ground.
Come to think of it, most heat loss from the earth must be from infra red, which will also come from the opaque ground much more than from the air.
mattreb@feddit.it 2 months ago
Yeah “dissipate away” is probably a bit misleading but I meant that the heat source is mainly the surface since it’s difficult to heat the thin outer layers directly, and from there heat moves up thorough ir radiation or adiabatic expansion. But it’s not like mountains are cooled down by adiabatic expansion, since the air wouldn’t move up without a temperature gradient, which means that it cannot get colder that the mountains already are. So I would think they are simply farther away form surface heat radiation and have thinner air that don’t assorb heat…
milicent_bystandr@lemm.ee 2 months ago
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.