FAA Aircraft Dispatcher (ADX)MeteorologyMedium
A dispatcher reviews an early morning temperature sounding at a departure airport and finds that temperature increases from the surface up to 3,000 feet before beginning a normal decrease with height. What atmospheric condition does this sounding depict, and what surface weather hazard is it most likely to promote?
- AA temperature inversion, favoring fog and trapped pollutants near the surface
- BA super-adiabatic layer, favoring severe thunderstorm formation
- CAn unstable lapse rate, favoring strong convective turbulence
- DA dry adiabatic layer, favoring rapid cumulus development
Show answer & explanationAnswer & explanation
Correct answer: A. A temperature inversion, favoring fog and trapped pollutants near the surface
An increase in temperature with height is, by definition, a temperature inversion, which represents an extremely stable layer of air. Inversions suppress vertical mixing, trapping moisture, smoke, and pollutants near the surface and are a primary contributor to radiation fog and poor visibility, especially during calm, clear early morning conditions.
Why the other options are wrong
- B. A super-adiabatic layer has an even steeper decrease than dry adiabatic, associated with instability, not inversions.
- C. An unstable lapse rate would show temperature decreasing rapidly with height, the opposite of what's described.
- D. A dry adiabatic layer refers to a specific 3°C/1000 ft cooling rate for rising unsaturated air, not a warming layer.
Temperature Inversion
A layer of the atmosphere in which temperature increases with height instead of decreasing, representing very stable air.
- Common near the surface on clear, calm nights (radiation inversion)
- Suppresses vertical mixing, trapping fog, haze, and pollutants
- Can also form aloft due to subsidence or frontal overrunning
Memory trick: Inversion = 'upside-down' temperature — it gets warmer, not colder, as you climb, trapping the bad stuff below.