Mountain Wave Turbulence

The central mountain range of the United States, often called the Rocky Mountains

Introduction

Mountain wave turbulence is a type of atmospheric turbulence that occurs when strong winds encounter a mountain range, forcing the air to rise and creating wave-like patterns that can cause strong up and downdrafts, potentially leading to severe turbulence for aircraft.

Formation

• Wind Flow: Mountain waves form when strong winds flow perpendicularly (or nearly so) to a mountain range.
• Air Lifting: The wind is forced to rise over the mountain, and as it ascends, it cools and may encounter a stable layer of air, leading to the formation of waves.
• Wave Patterns: These waves can extend horizontally and vertically, creating areas of both upward and downward air currents.

Conditions

Mountain waves are most likely to occur when:

• Winds are strong and blowing across a mountain range.
• There is a stable layer of air above the mountain.
• Wind speed increases with altitude.

Types

There are two main types of mountain waves:

• Trapped lee waves: These waves are trapped near the mountain and can extend hundreds of miles downwind.
• Vertically propagating waves: These waves can extend high into the atmosphere.

Effects on Aviation

• Turbulence: Mountain waves can create strong updrafts and downdrafts, leading to turbulence that can be hazardous for aircraft.
• Altitude Changes: Aircraft can experience rapid changes in altitude as they encounter the waves, making it difficult to maintain altitude.
• Airspeed Changes: The turbulence can also cause changes in airspeed, requiring pilots to make frequent corrections.
• Rotor Clouds: Below the crests of the waves, rotor clouds can form, which are areas of intense turbulence.
• Lenticular Clouds: Lenticular clouds, which are lens-shaped clouds, can also be associated with mountain waves.
• Downslope Windstorms: Mountain waves can also contribute to downslope windstorms like chinooks.

External Links

• APN