FAA Sport Pilot Airplane (SPA)WeatherMedium
During a preflight weather briefing, a pilot learns of smooth air, low stratus clouds, and visibility restricted by haze and smoke trapped near the surface. These conditions are most indicative of what type of air mass?
- AOccluded air mass
- BUnstable air mass
- CConvective air mass
- DStable air mass
Show answer & explanationAnswer & explanation
Correct answer: D. Stable air mass
Stable air resists vertical motion, producing smooth flying conditions, stratiform clouds, steady light precipitation, and poor surface visibility because pollutants and moisture are trapped near the ground rather than mixed upward.
Why the other options are wrong
- A. An occluded air mass is a frontal type, not a stability description.
- B. Unstable air produces cumuliform clouds, turbulence, and good visibility, the opposite of this scenario.
- C. 'Convective air mass' is not a standard term and implies instability, not stability.
Atmospheric Stability
A stable atmosphere resists vertical air movement, resulting in smooth air, stratiform clouds, and restricted visibility; an unstable atmosphere favors vertical currents, cumulus clouds, and turbulence.
- Stable air: smooth, stratiform clouds, poor visibility from trapped haze
- Unstable air: turbulent, cumuliform clouds, good visibility, showery precipitation
- Temperature inversions promote stability
Memory trick: 'Stable = Still and Smoggy'