FAA Private Pilot Airplane (PAR)Weather Theory and ServicesMedium
A pilot is conducting a preflight weather briefing for a cross-country flight. The briefing indicates a significant amount of moisture in the air and a temperature profile where the temperature decreases uniformly with increasing altitude, but at a rate less than the dry adiabatic lapse rate. This atmospheric condition is most conducive to which type of cloud formation?
- AStratiform clouds, often associated with widespread precipitation.
- BLenticular clouds, typically forming over mountainous terrain.
- CCumulonimbus clouds, indicating severe thunderstorms.
- DCirrus clouds, composed of ice crystals at high altitudes.
Show answer & explanationAnswer & explanation
Correct answer: A. Stratiform clouds, often associated with widespread precipitation.
When the atmosphere is stable, air parcels lifted will become cooler than the surrounding air and tend to sink back, inhibiting strong vertical development. A uniform decrease in temperature at a rate less than the dry adiabatic lapse rate indicates a stable atmosphere. With sufficient moisture, this stability favors the formation of stratiform clouds which spread horizontally.
Why the other options are wrong
- B. Lenticular clouds form due to mountain waves, which are a specific type of atmospheric disturbance, not directly implied by general stability and moisture.
- C. Cumulonimbus clouds require an unstable atmosphere to support strong vertical development.
- D. Cirrus clouds are high-level clouds and while they can form in stable conditions, the description more generally points to stratiform development at lower to mid-altitudes with 'significant moisture'. Forming at high altitudes, cirrus clouds consist of ice and thus require very cold conditions, not just general moisture and stability.
Stable Atmosphere Cloud Formation
In a stable atmosphere, vertically displaced air tends to return to its original position, leading to horizontal cloud development if moisture is present.
- Air parcels lifted in a stable atmosphere become cooler than surrounding air.
- This inhibits strong vertical cloud growth.
- If moisture is present, stratiform (layer-like) clouds are likely to form.
Memory trick: Stable air, like a calm lake, spreads its clouds flat and wide.