What action would increase the stability of an air mass?

Increasing the stability of an air mass primarily involves making it less likely to rise and develop into convective currents. Cooling from below is a key factor in enhancing stability because it causes the air at the surface to become denser than the air above it. This denser, cooler air is less buoyant, which inhibits upward motion.

When an air mass is cooled from below, especially near the surface, the air particles lose energy and their ability to ascend. This leads to conditions where air parcels are less likely to rise independently, which promotes stability within the air mass. In stable atmospheric conditions, the vertical movement of air is suppressed, often leading to a more stratified and layered cloud structure, rather than the development of towering cumulonimbus clouds typically associated with instability.

On the other hand, warming from above tends to promote instability, and reducing surface friction usually enhances mixing and turbulence, which can lead to a less stable atmosphere. Adding moisture can sometimes enhance instability as well, since it can lead to the formation of cumulus clouds and encourage convection. Thus, cooling from below is the most effective way to increase the stability of an air mass.