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Lenticular Cloud
Lenticular clouds (Latin: ''Lenticularis'' lentil-shaped, from ''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. Because of their unique appearance, they have been suggested as an explanation for some unidentified flying object (UFO) sightings. Formation and appearance 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 turb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harold's Cross
Harold's Cross () is an affluent urban village and inner suburb on the south side of Dublin, Ireland in the postal district D6W. The River Poddle runs through it, though largely in an underground culvert, and it holds a major cemetery, Mount Jerome, and Our Lady's Hospice. Location Harold's Cross is situated north of Terenure and Rathgar, west of Rathmines, east of Crumlin and Kimmage, and directly south from the Grand Canal at Clanbrassil Street. It lies within the jurisdiction of Dublin City Council, and straddles the boundary of Dublin 6, Dublin 6W and Dublin 12 postal districts. The Poddle The River Poddle runs south to north through the area. At the southern end of the district, the river's course splits at the centuries-old "Tongue" or "Stone Boat" with part of its flow diverted underground into the "City Watercourse" culvert, while the mainline continues overground, passing through ponds. The Poddle goes underground between Mount Argus and Mount Jerome, then flo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lee Waves
In meteorology, lee waves are atmospheric stationary waves. The most common form is mountain waves, which are atmospheric internal gravity waves. These were discovered in 1933 by two German glider pilots, Hans Deutschmann and Wolf Hirth, above the Krkonoše. They are periodic changes of atmospheric pressure, temperature and orthometric height in a current of air caused by vertical displacement, for example orographic lift when the wind blows over a mountain or mountain range. They can also be caused by the surface wind blowing over an escarpment or plateau, or even by upper winds deflected over a thermal updraft or cloud street. The vertical motion forces periodic changes in speed and direction of the air within this air current. They always occur in groups on the lee side of the terrain that triggers them. Sometimes, mountain waves can help to enhance precipitation amounts downwind of mountain ranges. Usually a turbulent vortex, with its axis of rotation parallel to the m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pileus (meteorology)
A pileus (; Latin for "cap"), also called scarf cloud or cap cloud, is a small, horizontal, lenticular cloud appearing above a cumulus or cumulonimbus cloud. Pileus clouds are often short-lived, with the main cloud beneath them rising through convection to absorb them. They are formed by strong updraft at lower altitudes, acting upon moist air above, causing the air to cool to its dew point. As such, they are usually indicators of severe weather, and a pileus found atop a cumulus cloud often foreshadows transformation into a cumulonimbus cloud, as it indicates a strong updraft within the cloud. Pilei can also form above mountains, ash clouds, and pyrocumulus clouds from erupting volcanoes. Pilei form above some mushroom clouds of high- yield nuclear detonations. Appearance Sometimes several pileus clouds are observed above each other. The bright iridescent colors seen in pileus are sunlight diffracted in water vapor. Iridescent colors are strongest when the diffracting drop ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cloud Appreciation Society
The Cloud Appreciation Society is a society founded by Gavin Pretor-Pinney from the United Kingdom in January 2005. The society aims to foster understanding and appreciation of clouds, and has over 50,000 members from 120 countries, as of March 2020. Yahoo! named the society's website as "the most weird and wonderful find on the internet for 2005". The group and its founder were the focus of a BBC documentary ''Cloudspotting'', based on Pretor-Pinney's book ''The Cloudspotter's Guide''. During an episode of ''Taskmaster'', comedian Hugh Dennis revealed he is a member of the society. In 2017, the Cloud Appreciation Society was credited with adding the Asperitas classification of cloud to the World Meteorological Organization's International Cloud Atlas. See also *"Both Sides, Now" *Cloudscape (art) *Cloudscape photography References External links * Article from Times Online* ''The New York Times ''The New York Times'' (''the Times'', ''NYT'', or the Gray Lady ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glider (sailplane)
A glider or sailplane is a type of glider aircraft used in the leisure activity and sport of gliding (also called soaring). This unpowered aircraft can use naturally occurring currents of rising air in the atmosphere to gain altitude. Sailplanes are aerodynamically streamlined and so can fly a significant distance forward for a small decrease in altitude. In North America the term 'sailplane' is also used to describe this type of aircraft. In other parts of the English-speaking world, the word 'glider' is more common. Types Gliders benefit from producing the least drag for any given amount of lift, and this is best achieved with long, thin wings, a slender fuselage and smooth surfaces with an absence of protuberances. Aircraft with these features are able to soar – climb efficiently in rising air produced by thermals or hills. In still air, sailplanes can glide long distances at high speed with a minimum loss of height in between. Sailplanes have rigid wings and eithe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gliding
Gliding is a recreational activity and competitive air sport in which pilots fly unpowered aircraft known as gliders or sailplanes using naturally occurring currents of rising air in the atmosphere to remain airborne. The word ''soaring'' is also used for the sport. Gliding as a sport began in the 1920s. Initially the objective was to increase the duration of flights but soon pilots attempted cross-country flights away from the place of launch. Improvements in aerodynamics and in the understanding of weather phenomena have allowed greater distances at higher average speeds. Long distances are now flown using any of the main sources of rising air: ridge lift, thermals and lee waves. When conditions are favourable, experienced pilots can now fly hundreds of kilometres before returning to their home airfields; occasionally flights of more than are achieved. Some competitive pilots fly in races around pre-defined courses. These gliding competitions test pilots' abilities to mak ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cloud Iridescence
Cloud iridescence or irisation is a colorful optical phenomenon that occurs in a cloud and appears in the general proximity of the Sun or Moon. The colors resemble those seen in soap bubbles and oil on a water surface. It is a type of photometeor. This fairly common phenomenon is most often observed in altocumulus, cirrocumulus, lenticular, and cirrus clouds. They sometimes appear as bands parallel to the edge of the clouds. Iridescence is also seen in the much rarer polar stratospheric clouds, also called nacreous clouds. The colors are usually pastel, but can be very vivid or mingled together, sometimes similar to mother-of-pearl. When appearing near the Sun, the effect can be difficult to spot as it is drowned in the Sun's glare. This may be overcome by shielding the sunlight with one's hand or hiding it behind a tree or building. Other aids are dark glasses, or observing the sky reflected in a convex mirror or in a pool of water. Etymology Irisations are named after t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Precipitation
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. Precipitation occurs when a portion of the atmosphere becomes saturated with water vapor (reaching 100% relative humidity), so that the water condenses and "precipitates" or falls. Thus, fog and mist are not precipitation but colloids, because the water vapor does not condense sufficiently to precipitate. Two processes, possibly acting together, can lead to air becoming saturated: cooling the air or adding water vapor to the air. Precipitation forms as smaller droplets coalesce via collision with other rain drops or ice crystals within a cloud. Short, intense periods of rain in scattered locations are called showers. Moisture that is lifted or otherwise forced to rise over a layer of sub-freezing air at the surface may be condensed into ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Updraft
In meteorology, an updraft is a small-scale current of rising air, often within a cloud. Overview Localized regions of warm or cool air will exhibit vertical movement. A mass of warm air will typically be less dense than the surrounding region, and so will rise until it reaches air that is either warmer or less dense than itself. The converse will occur for a mass of cool air, and is known as subsidence. This movement of large volumes of air, especially when regions of hot, wet air rise, can create large clouds, and is the central source of thunderstorms. Drafts can also be conceived by low or high pressure regions. A low pressure region will attract air from the surrounding area, which will move towards the center and then rise, creating an updraft. A high pressure region will attract air from the surrounding area, which will move towards the center and sink, spawning a downdraft. Updrafts and downdrafts, along with wind shear in general, are a major contributor to airplane cras ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wave Cloud
A wave cloud is a cloud form created by atmospheric internal waves. Formation The atmospheric internal waves that form wave clouds are created as stable air flows over a raised land feature such as a mountain range, and can form either directly above or in the lee of the feature. As an air mass travels through the wave, it undergoes repeated uplift and descent. If there is enough moisture in the atmosphere, clouds will form at the cooled crests of these waves. In the descending part of the wave, those clouds will evaporate due to adiabatic heating, leading to the characteristic clouded and clear bands. The cloud base on the leeward side is higher than on the windward side, because precipitation on the windward side removes water from the air.Wallace, John M., Hobbs, Peter V. Atmospheric Science, and Introductory Survey. San Diego, CA: Academic Press, 1977. It is possible that simple convection from mountain summits can also form wave clouds. This occurs as the convection ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dew Point
The dew point is the temperature to which air must be cooled to become saturated with water vapor, assuming constant air pressure and water content. When cooled below the dew point, moisture capacity is reduced and airborne water vapor will condense to form liquid water known as dew. When this occurs via contact with a colder surface, dew will form on that surface. The dew point is affected by humidity. When there is more moisture in the air, the dew point is higher. When the temperature is below the freezing point of water, the dew point is called the frost point, as frost is formed via deposition rather than condensation. In liquids, the analog to the dew point is the cloud point. Humidity If all the other factors influencing humidity remain constant, at ground level the relative humidity rises as the temperature falls; this is because less vapor is needed to saturate the air. In normal conditions, the dew point temperature will not be greater than the air temperature, sinc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leeward
Windward () and leeward () are terms used to describe the direction of the wind. Windward is ''upwind'' from the point of reference, i.e. towards the direction from which the wind is coming; leeward is ''downwind'' from the point of reference, i.e. along the direction towards which the wind is going. The side of a ship that is towards the leeward is its "lee side". If the vessel is heeling under the pressure of crosswind, the lee side will be the "lower side". During the Age of Sail, the term ''weather'' was used as a synonym for ''windward'' in some contexts, as in the ''weather gage''. Because it captures rain, the windward side of a mountain tends to be wet compared to the leeward it blocks. Origin The term "lee" comes from the middle-low German word // meaning "where the sea is not exposed to the wind" or "mild". The terms Luv and Lee (engl. Windward and Leeward) have been in use since the 17th century. Usage Windward and leeward directions (and the points ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
