FAA Private Pilot Airplane (PAR)Weather Theory and ServicesEasy
A pilot notes that during a climb through 5,000 feet the outside air temperature increases from 10°C to 14°C instead of decreasing. What atmospheric condition does this describe?
- AAn unstable lapse rate
- BThe standard lapse rate
- CA temperature inversion
- DA dry adiabatic lapse rate
Show answer & explanationAnswer & explanation
Correct answer: C. A temperature inversion
Temperature normally decreases with altitude at the standard lapse rate of about 2°C per 1,000 feet. When temperature instead increases with altitude, this is called a temperature inversion, often producing very stable air and poor visibility near the surface.
Why the other options are wrong
- A. Unstable air is characterized by temperature decreasing faster than standard, not increasing.
- B. The standard lapse rate is a decrease of about 2°C per 1,000 feet, the opposite of what occurred.
- D. The dry adiabatic lapse rate also describes cooling with altitude, not warming.
Temperature Inversion
A layer of the atmosphere in which temperature increases with altitude instead of decreasing, often trapping smoke, haze, and fog near the surface.
- Common on clear, calm nights due to surface radiational cooling
- Creates very stable air, suppressing vertical motion
- Can trap pollutants and moisture, reducing surface visibility
Memory trick: Inversion = temp goes the WRONG way (up, not down)