What characterizes stable air?

Stable air is characterized by the tendency of air parcels to return to their original position after being displaced. This stability is due to the vertical temperature gradient; in stable conditions, cooler air is sitting atop warmer air. When air is lifted, it will cool and become denser than the surrounding air, causing it to sink back to its original level. This behavior prevents the air from continuing to rise, which is a key feature of stability.

In this context, the other options reflect different characteristics of air movement not associated with stability. For instance, when air is pushed up and continues to rise, it indicates instability, as it suggests that the perturbed air is warmer and less dense than its surroundings. If air stays at the same level, it implies a lack of movement but does not fully encapsulate the idea of stability since it may not account for the response to upward movement. Similarly, the description of air cooling too quickly might indicate rapid changes in temperature that are more typical of an unstable atmosphere, where buoyancy can lead to upward growth of clouds and turbulence rather than the returning behavior seen in stable conditions.