2 ms·

I don't find the debunking article persuasive. It says, "Imagine you take a blob of warm air from the surface up to some height... this transformation has to ch

I don't find the debunking article persuasive. It says, "Imagine you take a blob of warm air from the surface up to some height... this transformation has to change the temperature of the air in the blob." No it doesn't. The nearest it gets to supporting that claim is, "It turns out to be very easy to derive an equation that says that the temperature decreases by 10 degrees C per about 1000 m of height with no vertical motion. That explains why the air above the surface is colder than the air at the surface." I'd like to see the assumptions of deriving that equation. Without seeing how the equation is derived we can't jump straight to the "That explains why" part. I guess the equation he's talking about assumes the atmosphere is static and is simply deals with how the upper atmosphere is colder because it can radiate into space, whereas the lower atmosphere can only exchange radiation with warm ground or the cold-but-still-warmer-than-space upper atmosphere. If so, it says nothing about what happens when you "move a blob of warm air". Maybe building these things is not feasible or maybe the effect is not significant, but it doesn't look physically impossible to me.

frede 9y ago
The air cools down when raising in the chimney because the air pressure decreases, leading to adiabatic expansion.
kashkhan 9y ago
when any gas expands, it does work in expanding against the outside "surface" of the control volume, which comes from the internal energy - temperature - of the molecules. The equations are commonly derived in thermodynamics undergrad courses. look up adiabatic expansion. here's a video: https://www.youtube.com/watch?v=ObnWb7yspxA https://www.youtube.com/watch?v=ObnWb7yspxA
- abainbridge 9y ago
  Good point. I stand corrected. I still think that the radiating-into-space effect I mentioned is real. I imagine this is part of the reason there is convection in the atmosphere. But I'm out of my depth.

frede 9y ago

The air cools down when raising in the chimney because the air pressure decreases, leading to adiabatic expansion.

kashkhan 9y ago

when any gas expands, it does work in expanding against the outside "surface" of the control volume, which comes from the internal energy - temperature - of the molecules. The equations are commonly derived in thermodynamics undergrad courses. look up adiabatic expansion. here's a video: https://www.youtube.com/watch?v=ObnWb7yspxA https://www.youtube.com/watch?v=ObnWb7yspxA

abainbridge 9y ago
Good point. I stand corrected. I still think that the radiating-into-space effect I mentioned is real. I imagine this is part of the reason there is convection in the atmosphere. But I'm out of my depth.