Lenticular cloud

{{Infobox cloud

| name = Lenticular cloud

| image location = Lenticular Cloud over Harold's Cross Dublin Ireland 30-6-15.jpg

| image name = Dramatic lenticular cloud formation over Harold's Cross, Dublin

| abbreviation =

| symbol =

| genus = stratocumulus, altocumulus, cirrocumulus

| species = lenticularis (Latin: lentil)

| variety =

| altitude_m = up to 12,000

| altitude_ft = 40,000

| level = low, middle, high

| appearance = lens-like, saucer-shaped

| precipitation = virga only

| thickness =

| ice content =

}}

File:Pressure ridges Scott Base lrg.jpg]]

Lenticular clouds ({{etymology|la|{{wikt-lang|la|lenticularis}}|lentil-shaped}}, {{etymology||{{wikt-lang|la|lenticula}}|lentil}}) are stationary clouds that form mostly in the troposphere, typically in parallel alignment to the wind direction. They are often comparable in appearance to a lens or saucer. Nacreous clouds that form in the lower stratosphere sometimes have lenticular shapes.

There are three main types of lenticular clouds: altocumulus standing lenticular (ACSL), stratocumulus standing lenticular (SCSL), and cirrocumulus standing lenticular (CCSL), varying in altitude above the ground.

Formation and appearance

File:Mayon Volcano with cloudy hat.jpg, Philippines.]]

As air travels along the surface of the Earth, obstructions are often encountered, including natural features, such as mountains or hills, and artificial structures, such as buildings and other constructions, which disrupt the flow of air into "eddies", or areas of turbulence.

When moist, stable air flows over a larger eddy, such as those caused by mountains, a series of large-scale standing waves form on the leeward side of the mountain. If the temperature at the crest of the wave drops below the dew point, moisture in the air may condense to form lenticular clouds. Under certain conditions, long strings of lenticular clouds may form near the crest of each successive wave, creating a formation known as a "wave cloud". Those wave systems can produce large updrafts, occasionally enough for water vapour to condense and produce precipitation.{{cite web| title=Altocumulus Standing Lenticular Clouds| url=https://www.weather.gov/abq/features_acsl|website=National Weather Service |publisher=NOAA| access-date=9 March 2018}}

Lenticular clouds have been said to be mistaken for UFOs, because many of them have the shape of a "flying saucer", with a characteristic "lens" or smooth, saucer-like shape. Lenticular clouds generally do not form over low-lying or flat terrain, so many people may have never seen one before and don't know that they can exist.{{cite web|last1=Byrd |first1=Deborah |title=Lenticular clouds look like UFOs| url=http://earthsky.org/earth/best-photos-beautiful-lenticular-clouds-around-the-world |website=EarthSky| date=19 January 2021 |access-date=3 May 2022}}{{refn| group=nb| Lenticular 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.}} Bright colours (called iridescence) are sometimes seen along the edge of lenticular clouds.[http://www.atoptics.co.uk/droplets/irid1.htm Atmospheric Optics: Iridescent Clouds]

Flight

Pilots of powered aircraft tend to avoid flying near lenticular clouds because of the turbulence and sinking air of the rotor generated at the trailing edge of these clouds, but glider pilots actively seek them out in order to climb in the upward moving air at the leading edge. 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 to cover great distances. {{As of| 2020}}, the gliding world records for both distance (over 3,000 km; 1,864 mi){{Cite web |date=2017-10-10 |title=Klaus Ohlmann (GER) (7605) {{!}} World Air Sports Federation |url=https://www.fai.org/record/7605 |access-date=2022-11-22 |website=www.fai.org |language=en}} and absolute altitude (over 22,000 metres; 74,334 ft){{Cite web| date=2017-08-03 |title=Records| url=https://www.fai.org/page/igc-records| access-date=2020-10-05 |website=www.fai.org|language=en}} were set using such lift.{{Citation needed|date=October 2020}}

Notes

References

External links

[http://www.premierflightct.com/newsletters/TrainingArticles/StandingLenticularClouds.html Standing Lenticular Clouds]

[https://www.youtube.com/watch?v=OZwp34fuEDY&list=PLfHkfaV5x0UGdoQnCs_iBycE3FyITeTtf Time Lapse of Lenticulars courtesy The Weather Nutz]

[https://www.bbc.co.uk/news/uk-england-leeds-16302606 BBC image gallery of lenticular clouds over Yorkshire in 2011]
[http://commons.wikimedia.org/wiki/File:Lenticular_cloud_jmusil.jpg Lenticular cloud seen from Palm Desert, California, in April 2008]
[http://www.kcocco.com/index.php?entry=entry070219-225315 kcocco.com Altocumulus Lenticular Clouds, Wasatch Mountains, Utah]
{{APOD |date=21 January 2009 |title=Picture of the Day 2009-01-21: A lenticular Cloud over New Zealand}}
{{cite news

|url=http://www.komonews.com/weather/blog/35631614.html

|access-date=2008-12-11

|title=Mt. Rainier puts on a show!

|first=Scott

|last=Sistek

|publisher=KOMONews.com}}

{{APOD |date=3 February 2009 |title=Lenticular Clouds near Mt. Ranier, Washington, USA}}
[https://www.flickr.com/photos/schuberts/554160340 San Francisco's Richmond District 2007: "Lennies" attacking the Richmond]

Category:Cumulus

Category:Articles containing video clips