Lenticular cloud

Famous for their UFO-like shape, lenticular clouds have captured public imagination and frequently appear in photography and popular media. They serve as vivid illustrations of atmospheric wave phenomena in educational materials and are sometimes informally called "saucer clouds" or "UFO clouds." Their striking form has inspired artistic and cultural references worldwide.

• Lenticular clouds are often mistaken for flying saucers due to their smooth, lens-like shape.
• They can form at various altitudes, from low-level Stratocumulus to high-level Cirrocumulus types.
• These clouds remain stationary despite strong winds flowing through them, a unique behavior linked to atmospheric gravity waves.
• They may exhibit iridescence and sometimes develop accessory features like pileus caps or virga.
• Commonly found over mountainous regions such as the Rockies, Andes, Alps, and Japanese Alps.

🌦️ Lenticular clouds form when stable, moist air flows over a mountain or hill, creating atmospheric gravity waves on the lee side. As the air rises at the wave crest, it cools adiabatically, reaching saturation and condensing into cloud droplets. The cloud forms at the wave peak and dissipates as the air descends and warms, resulting in a stationary cloud that appears fixed despite continuous airflow. This process requires stable atmospheric conditions, sufficient moisture, and an orographic obstacle to generate the wave pattern.

🗺️ Lenticular clouds primarily occur at mid-level altitudes, typically between 500 and 6,000 meters at their base, extending up to 12,000 meters at their top depending on the genus. Altocumulus lenticularis generally form between 2,000 and 7,000 meters, Stratocumulus lenticularis between 500 and 2,000 meters, and Cirrocumulus lenticularis between 6,000 and 12,000 meters. They are most prevalent in mountainous regions worldwide, including the Rockies, Andes, Alps, and Japanese Alps, but can also appear over hills or areas with strong wind shear and wave activity.

⚠️ While lenticular clouds themselves do not produce precipitation, they are associated with severe turbulence caused by underlying mountain waves. This turbulence can pose significant hazards to aviation, especially for glider pilots and mountain flying. Additionally, rotor clouds and wind shear may develop beneath lenticular clouds, increasing the risk of sudden and dangerous air movements. Pilots are trained to recognize these clouds as warnings to exercise caution.

🔍 Lenticular clouds are primarily observed visually due to their distinctive shape and stationary behavior. Ground-based photography and human observation remain key methods for identification. Remote sensing techniques include satellite imagery, which captures their smooth, oval shapes; ceilometers and lidar instruments that measure vertical cloud structure; and radar systems that can detect associated atmospheric waves. These combined methods help meteorologists monitor their formation and implications.

🛰️ In satellite imagery, lenticular clouds appear as smooth, oval, or elongated white patches, often aligned perpendicular to the prevailing wind direction. They remain stationary relative to the underlying terrain, making them distinguishable from other cloud types. Visible satellite bands highlight their sharp edges and layered structure, while infrared imagery can reveal temperature contrasts associated with their altitude and phase. Their unique shape and persistence aid in remote identification of mountain wave activity.