Which factor would increase the stability of an air mass?

Cooling from below is a critical factor that increases the stability of an air mass. When an air mass cools from below, the temperature of the surface layer drops, which can lead to a reduction in the ability of air parcels to rise. For an air mass to remain stable, it needs to have the lower layers cooler than the upper layers. This condition inhibits vertical movement because the cooler air is denser, leading to a tendency for the air to remain in place rather than rise.

In contrast, if the air is warmed from below, it becomes less stable since warmer air is less dense than cooler air, promoting vertical movement and possibly leading to convection. Similarly, a decrease in water vapor does not directly correlate with increased stability; in fact, moisture generally contributes to the potential for instability, especially when it cools. Increased humidity at higher altitudes may lead to instability as well by enhancing condensation and cloud formation, which can trigger atmospheric lifting and turbulence. Therefore, cooling from below is key for enhancing the stability of an air mass.