Definition
The rate at which air temperature decreases with an increase in altitude. The standard (average) lapse rate in the atmosphere is approximately 2 degrees Celsius (3.5 degrees Fahrenheit) per 1,000 feet of altitude gained.
Plain English
How quickly the air gets colder as you climb. On an average day, the air cools by about 2 degrees Celsius for every 1,000 feet you go up.
Context Anchor
Pilots encounter temperature lapse rate in weather discussions, performance planning, and explanations of why airplane performance changes with altitude and temperature.
Derivation
Lapse comes from the Latin lapsus, meaning a slip or gradual fall. Here it refers to the steady falling-off of temperature as altitude increases.
Why Pilots Care
A steeper or shallower lapse rate changes air density and engine performance, directly affecting takeoff distance, climb rate, and service ceiling.
Grounding Statement
Climbing through the atmosphere is like walking up a mountain — the higher you go, the colder the air gets, and the lapse rate tells you how fast that cooling happens.
Intuition Check
Do not read “lapse” as a mistake or a time limit here. In this term, it means a change in temperature with altitude, usually a drop as you climb.
Example Sentence 1
Using the standard temperature lapse rate, the pilot estimated the outside air temperature at 8,000 feet would be about 16 degrees Celsius cooler than at the surface.
Example Sentence 2
When the actual lapse rate proved steeper than standard, the airplane climbed faster than the performance charts had predicted.