What causes mountain waves to form?

Mountain waves are primarily generated when stable air flows over mountains or other significant terrain features. As the wind encounters these obstacles, it is forced to rise, and this uplift creates a wave-like pattern in the atmosphere. The correct answer focuses on the effect of the wind interacting with the terrain, causing it to leave vortices, or a series of eddies in its wake.

These vortices can lead to significant turbulence and oscillations downwind of the mountains, characteristics typical of mountain wave activity. This phenomenon can be particularly dangerous for aircraft because the resulting turbulence can extend far downwind from the mountain ridges.

The other factors mentioned do not directly contribute to the formation of mountain waves. While an increase in air pressure can affect weather patterns, it doesn't specifically cause the waves associated with mountainous terrain. Similarly, the dynamics of warmer air moving over colder air or the formation of clouds at high altitudes may relate to different meteorological processes, but they do not encapsulate the mechanism of mountain wave formation as effectively as the interaction of wind with the terrain does.