weather theoryFAA-published sample question (CAX, Aug 2021)
What are the characteristics of an unstable atmosphere?
A
A cool, dry air mass.
B
A warm, humid air mass.✓ Correct Answer
C
Descending air in the northern hemisphere.
Explanation
PHAK Chapter 12 explains that warm, moist air is the most unstable combination: warm air is buoyant and moisture releases latent heat as it condenses, so rising air keeps rising. A cool, dry air mass tends to be stable, and descending (subsiding) air warms and stabilizes the atmosphere rather than destabilizing it.
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