What is the lapse rate?

The lapse rate refers to the rate at which temperature decreases with altitude in the atmosphere. As you ascend in the atmosphere, the temperature typically decreases, and this decrease can vary based on conditions such as humidity and the surrounding environment. In the standard atmosphere, the average lapse rate is about 6.5 degrees Celsius per kilometer of ascent in the troposphere. Understanding the lapse rate is crucial for pilots and meteorologists, as it affects weather patterns, aircraft performance, and stability of the atmosphere.

While humidity and pressure also change with altitude—humidity typically decreases while pressure drops—the specific term "lapse rate" is explicitly defined in relation to temperature variation. Atmospheric stability is related but focuses on the tendency for air to rise or sink, which is influenced by the lapse rate, but is not a direct description of it.