Lenticular cloud

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Lenticular cloud
Dramatic "saucer cloud" over Campbell Mesa, Flagstaff, Arizona
Dramatic "saucer cloud" over Campbell Mesa, Flagstaff, Arizona
Genus Stratocumulus, altocumulus, cirrocumulus
Species lenticularis (Latin: lens-shaped)
Altitude up to 12,000 m
(up to 40,000 ft)
Appearance lens-like, UFO-shaped
Precipitation cloud? Sometimes

Lenticular clouds (Altocumulus lenticularis) are stationary lens-shaped clouds that form in the troposphere, normally in perpendicular alignment to the wind direction. Lenticular clouds can be separated into altocumulus standing lenticularis (ACSL), stratocumulus standing lenticular (SCSL), and cirrocumulus standing lenticular (CCSL). Because of their shape, they have been offered as an explanation for some Unidentified Flying Object (UFO) sightings.

Formation[edit]

Where stable moist air flows over a mountain or a range of mountains, a series of large-scale standing waves may form on the downwind side. If the temperature at the crest of the wave drops to the dew point, moisture in the air may condense to form lenticular clouds. As the moist air moves back down into the trough of the wave, the cloud may evaporate back into vapor. Under certain conditions, long strings of lenticular clouds can form near the crest of each successive wave, creating a formation known as a "wave cloud." The wave systems cause large vertical air movements and so enough water vapor may condense to produce precipitation. The clouds have been mistaken for UFOs (or "visual cover" for UFOs), particularly the round "flying saucer"-type, because these clouds have a characteristic lens appearance and smooth saucer-like shape; also, because lenticular clouds generally do not form over low-lying or flat terrain, many people have never seen one and are not aware clouds with that shape can exist. Bright colors (called irisation) are sometimes seen along the edge of lenticular clouds.[1] These clouds have also been known to form in cases where a mountain does not exist, but rather as the result of shear winds created by a front.

Flight[edit]

Pilots of powered aircraft tend to avoid flying near lenticular clouds because of the turbulence of the rotor systems that accompany them, but glider pilots actively seek them out. The precise location of the rising air mass is fairly easy to predict from the orientation of the clouds. "Wave lift" of this kind is often very smooth and strong, and enables gliders to soar to remarkable altitudes and great distances. The current gliding world records for both distance (over 3,000 km; 1,864 mi) and altitude (15,460 m; 50,721 ft) were set using such lift.[2]

Altocumulus lenticularis Gallery[edit]

See also[edit]

References[edit]

External links[edit]