FAA Ground School Practice Test

What are characteristics of a moist, unstable air mass?

1. Stratus clouds and light rain

2. Cumuliform clouds and showery precipitation

3. Stable weather patterns

4. Dry air with high visibility

The correct answer is: Cumuliform clouds and showery precipitation

A moist, unstable air mass is characterized by its capacity for vertical movement, which leads to the development of clouds with significant vertical growth. This vertical development is typically represented by cumulus or cumulonimbus clouds, which can produce showery or convective precipitation. The instability of the air results from warm air rising quickly through the cooler surrounding air, often leading to turbulence, thunderstorm development, and localized heavy rain showers. In contrast, stratus clouds associated with light rain reflect a more stable air mass where air does not rise significantly, indicating a lack of instability. Similarly, stable weather patterns do not support the characteristics of moist, unstable air, which is marked by active weather changes. Lastly, dry air with high visibility indicates a stable condition where moisture content is low and does not support the formation of clouds and precipitation. Thus, the presence of cumuliform clouds and showery precipitation is a clear indicator of the moist, unstable nature of the air mass.