A Stable Lapse Rate is defined as less than how many degrees?

A Stable Lapse Rate is defined as less than how many degrees?

• A. Less than 5.5 degrees
• B. Greater than 5.5 degrees
• C. Exactly 5.5 degrees
• D. Cannot determine

Answer: (A)

Stability in the atmosphere is about how quickly temperature falls with height. A stable lapse rate means that as you go up, the temperature drops only a little. In this context, when the lapse rate is less than 5.5 degrees per 1,000 feet, the environment is stable: a parcel of air that rises will cool and become cooler (and denser) than its surroundings, so it tends to sink back down rather than continue rising. That makes vertical motion difficult and the atmosphere stable. If the lapse rate were greater than 5.5, rising air would stay warmer than its surroundings and continue to rise, indicating instability.

Stability in the atmosphere is about how quickly temperature falls with height. A stable lapse rate means that as you go up, the temperature drops only a little. In this context, when the lapse rate is less than 5.5 degrees per 1,000 feet, the environment is stable: a parcel of air that rises will cool and become cooler (and denser) than its surroundings, so it tends to sink back down rather than continue rising. That makes vertical motion difficult and the atmosphere stable. If the lapse rate were greater than 5.5, rising air would stay warmer than its surroundings and continue to rise, indicating instability.