What happens to an altimeter in cold weather? I put mine in the freezer to find out

[FlightInsight]

I had a hard time figuring out why the altimeter does what it does in cold weather. Hopefully this video clarifies things.
Dan, CFI

 

[PeterNSteinmetz]

. The relevant column of air would be the entire column pushing down due to gravity, which would be all the way out to the outer boundary layer of our atmosphere. If that column of air were to shrink in height due to a change in temperature, would that not create a void at the top of that column into which more air from the surrounding area would be pulled by gravity, thereby filling that void and bringing the height (and weight) of the column back up up, thus generating more pressure?

This sort of problem always puzzled me as well for basically the same reasons.

The answer is that the atmosphere is not in an equilibrium situation. I like to think of it like waves on the ocean. If you are underwater laying on the ground there as waves roll into shore, the height of the water above you does indeed vary. The same thing happens on the synoptic scale in the atmosphere, as both the height of the air column (measured to a certain pressure level) and it’s temperature (and therefore density) vary.

This happens because of friction and the viscosity of air, so the air doesn’t instantly flow in to fill in the gaps. Also relevant is the finite speed of transfer of heat through the air. So it is a non equilibrium situation.