FAA Aircraft Dispatcher (ADX)MeteorologyMedium
A dispatcher reviewing a temperature sounding notes an abrupt change from a decreasing to a near-isothermal or slightly increasing temperature trend with height at approximately 35,000 feet. This boundary marks the:
- AFreezing level, where temperature crosses 0°C
- BMesopause, marking the top of the mesosphere near 50 miles altitude
- CBase of the jet stream core, which is always located at a fixed altitude worldwide
- DTropopause, which separates the troposphere from the stratosphere and is typically lower and colder near the poles than at the equator
Show answer & explanationAnswer & explanation
Correct answer: D. Tropopause, which separates the troposphere from the stratosphere and is typically lower and colder near the poles than at the equator
The tropopause is the boundary between the troposphere and stratosphere, marked by an abrupt change from decreasing temperature with height to near-isothermal or slightly increasing temperature. Its height varies with latitude and season, typically being higher and warmer at the equator and lower and colder near the poles.
Why the other options are wrong
- A. The freezing level is defined by temperature value, not by a lapse rate discontinuity.
- B. The mesopause is far higher (~50 miles) and unrelated to this altitude range.
- C. The jet stream's altitude varies with the tropopause height and is not fixed.
Tropopause
The boundary layer separating the troposphere from the stratosphere, marked by a sharp change in the temperature lapse rate; its height varies with latitude and season.
- Higher (~55,000 ft) and warmer at the equator; lower (~25,000-30,000 ft) and colder at the poles
- Marked by transition from decreasing to isothermal/increasing temperature with height
- Closely associated with the position of the jet stream
Memory trick: Tropopause = the 'ceiling' of weather, where temperature stops falling