Definition
The decrease in temperature of a parcel of air caused by expansion as it rises into lower-pressure surroundings, with no heat exchanged between the parcel and the air around it.
Plain English
When air rises, the pressure on it drops, so it expands. The act of expanding cools it down — even though no heat is being added or taken away.
Context Anchor
Seen in weather and atmospheric stability discussions, especially when explaining rising air, cloud formation, and air moving over terrain.
Derivation
From the Greek 'adiabatos,' meaning 'not to be passed through' — referring to heat not passing in or out. The cooling happens purely from the air expanding, not from heat escaping.
Why Pilots Care
Understanding this process helps predict where clouds, turbulence, or icing may form during flight.
Grounding Statement
Think of a parcel of air being pushed up a mountain slope: as it rises into thinner air, it expands and cools, and if it cools enough, the moisture in it condenses into a cloud.
Intuition Check
Cooling does not always mean heat was taken away. In adiabatic cooling, the temperature drops because rising air expands as outside pressure decreases.
Example Sentence 1
As the moist air was forced up the windward side of the mountains, adiabatic cooling caused clouds to form along the ridgeline.
Example Sentence 2
The pilot noted that adiabatic cooling at higher altitudes could lead to unexpected icing in clear air.