What wind condition is most favorable for mountain wave formation?

What wind condition is most favorable for mountain wave formation?

• A. Across the ridge at 15-25 knots
• B. Directly up the slope at 40 knots
• C. Light and variable wind
• D. Downsloping warm wind

Answer: (A)

Mountain waves form when stable air flows perpendicular to a mountain range, forcing air to rise over the ridge and then descend in a repeating pattern downwind. A steady cross-ridge wind provides the right amount of energy and forcing to create those waves, especially at a moderate speed like about 15–25 knots, which is enough to lift air over the terrain without washing out the wave pattern. If the wind goes straight up the slope, the flow tends to lift air mainly over the ridge instead of setting up a downstream standing wave train. Light and variable winds don’t supply a consistent forcing to generate organized waves, and downslope warm winds tend to suppress vertical motion and reduce wave formation. So the best condition is a steady cross-ridge wind of modest speed.

Mountain waves form when stable air flows perpendicular to a mountain range, forcing air to rise over the ridge and then descend in a repeating pattern downwind. A steady cross-ridge wind provides the right amount of energy and forcing to create those waves, especially at a moderate speed like about 15–25 knots, which is enough to lift air over the terrain without washing out the wave pattern. If the wind goes straight up the slope, the flow tends to lift air mainly over the ridge instead of setting up a downstream standing wave train. Light and variable winds don’t supply a consistent forcing to generate organized waves, and downslope warm winds tend to suppress vertical motion and reduce wave formation. So the best condition is a steady cross-ridge wind of modest speed.