What is a significant characteristic of stable air?

A significant characteristic of stable air is indeed poor visibility. Stable air typically resists vertical motion due to its stratified nature, which can lead to the accumulation of moisture and pollutants near the surface. This stagnation creates conditions conducive to fog, haze, or low cloud cover, reducing visibility significantly.

In contrast, rapid fluctuations in temperature or unstable temperature gradients are associated with unstable air masses, which tend to promote convection and vertical growth of clouds. High wind speeds are generally more characteristic of unstable air conditions as well, where turbulence can enhance mixing and prevent stratification. Therefore, poor visibility stands out as a hallmark of stable air, reflecting its tendency to trap moisture and inhibit the development of convective activity.