Instrument Rating Checkride Practice Test

Unstable air is characterized by turbulent conditions primarily due to its tendency to rise and create vertical motion. This turbulence occurs because unstable air parcels, when lifted, can continue to rise due to their lower density compared to the surrounding air. As these parcels ascend, they cool and, if they reach saturation, can lead to the development of cumulus clouds and convective activity, which adds to the turbulence.

In contrast, stable air tends to suppress vertical motion, leading to smoother and more stratified layers. Calm air refers to conditions with little to no wind, which typically results in less turbulence. The term "heavy air" is not a standard meteorological term related to turbulence and does not accurately describe a specific atmospheric condition. Therefore, unstable air is the correct answer due to its inherent instability and the conditions that foster turbulence.