1.
Harold's Cross
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Harolds Cross is an urban village and inner suburb on the south side of Dublin, Ireland. Harolds Cross is situated north of Terenure and Rathgar, west of Rathmines, east of Crumlin and Kimmage and it lies within the jurisdiction of Dublin City Council, and straddles the boundary of Dublin 6, Dublin 6W and Dublin 12 postal districts. One explanation of the origin of the name Harolds Cross is that it is derived from the given to a gallows. Harolds Cross was a ground for the city of Dublin during the 18th century. In the 14th century the gallows there was maintained by the Archbishop, Harolds Cross stands on lands which formed, like those of Rathmines, part of the Manor of St. The De Meones family, who gave their name to Rathmines, Harolds Cross has a number of cafes, bars, shops, businesses and an active credit union. Harolds Cross Park, a well maintained city park, occupies the site of the original village green. At one side of Harolds Cross is Mount Jerome Cemetery, as mentioned in Joyces Ulysses, the remains of French Huguenots once buried in St. Peters Churchyard, Peters Row, which was demolished in the 1980s, are interred here. Other famous graves include those of mathematician William Rowan Hamilton and playwright John Millington Synge, the cemetery was operated from 1837 to 1984 by a private company and now belongs to the Massey family. The suburb is home to Dublins first hospice, Our Ladys Hospice. This palliative care facility was founded in 1879 in a house called Our Ladys Mount, Mary Aikenhead, founder of the Sisters of Charity order, lived in Our Ladys Mount from 1845 onwards. A new Hospice building was commenced in 1886, and many more buildings followed, the memorial cross at Harolds Cross was sculpted by local Sculptor/stonemason Mr Joseph Courtney. His father, Patrick Courtney, was also a sculptor and worked on the altar and stone works of St. Augustine & St. John the Baptist or Johns Lane in Thomas Street. In 1804 the sisters of the order of St. Clare moved to the village to run an orphanage, founded the previous year, now the Saint Clares Convent. St. Clares was founded in 1803 and as such is the oldest Catholic school in the Archdiocese of Dublin, beside the convent is the national headquarters for the Secular Franciscan Order. Harolds Cross is well served by transport, Dublin Bus routes 9,16,18,49. Dublin Bus also provides a Dublin Bus Nitelink service that operates the route as the 49 on Friday, Saturday nights. The area holds Saint Clares Convent and Primary School, Scoil Malóga, Harolds Cross National School, Our Lady of the Rosary Roman Catholic church and Mount Argus Monastery and it also has long-established links with the Garda Síochána and it was officially the church of the Dublin Metropolitan Police
2.
Saucer
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A saucer is a type of small dishware. The center of the saucer often contains a depression sized to fit a matching cup, this depression is sometimes raised, and antique saucers may omit it altogether. The saucer also provides a convenient place for a damp spoon, some animals, including cats, may also be fed from bowl-shaped saucers. A set of four is typical for a tea set, saucers have very little direct influence on beverage cooling rate, cups typically have low contact area with the saucer, so the heat transfer rate is low. For hot, water based beverages, cooling rate in a cup is typically dominated by evaporation, placing a saucer on top of a cup prevents such evaporative cooling taking place and is thus an effective way of reducing the cooling rate so that the drink remains warmer for longer. The reduction in heat loss due to evaporation is much greater than the increase in heat loss associated with conduction through the saucer. Coaster, used to protect the surface where the user might place a beverage Demitasse
3.
Mombacho
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Mombacho is a stratovolcano in Nicaragua, near the city of Granada. The Mombacho Volcano Nature Reserve is one of 78 protected areas of Nicaragua, Mombacho is not an extinct volcano but the last eruption occurred in 1570. There is no knowledge of earlier eruptions. The highest regions of the volcano are home to a cloud forest and dwarf forest, an increasingly popular tourist attraction, the volcano has fantastic views of Lake Nicaragua and the city of Granada. The volcano also has two hiking trails, a one that circles the main crater, and another, more difficult trail. The more difficult trail is the way to see some features such as the dwarf forest. The trail is almost completely 45° inclines and declines for about two miles, more than 700 different plants are registered around Mombacho, including many species of orchids
4.
Latin
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Latin is a classical language belonging to the Italic branch of the Indo-European languages. The Latin alphabet is derived from the Etruscan and Greek alphabets, Latin was originally spoken in Latium, in the Italian Peninsula. Through the power of the Roman Republic, it became the dominant language, Vulgar Latin developed into the Romance languages, such as Italian, Portuguese, Spanish, French, and Romanian. Latin, Italian and French have contributed many words to the English language, Latin and Ancient Greek roots are used in theology, biology, and medicine. By the late Roman Republic, Old Latin had been standardised into Classical Latin, Vulgar Latin was the colloquial form spoken during the same time and attested in inscriptions and the works of comic playwrights like Plautus and Terence. Late Latin is the language from the 3rd century. Later, Early Modern Latin and Modern Latin evolved, Latin was used as the language of international communication, scholarship, and science until well into the 18th century, when it began to be supplanted by vernaculars. Ecclesiastical Latin remains the language of the Holy See and the Roman Rite of the Catholic Church. Today, many students, scholars and members of the Catholic clergy speak Latin fluently and it is taught in primary, secondary and postsecondary educational institutions around the world. The language has been passed down through various forms, some inscriptions have been published in an internationally agreed, monumental, multivolume series, the Corpus Inscriptionum Latinarum. Authors and publishers vary, but the format is about the same, volumes detailing inscriptions with a critical apparatus stating the provenance, the reading and interpretation of these inscriptions is the subject matter of the field of epigraphy. The works of several hundred ancient authors who wrote in Latin have survived in whole or in part and they are in part the subject matter of the field of classics. The Cat in the Hat, and a book of fairy tales, additional resources include phrasebooks and resources for rendering everyday phrases and concepts into Latin, such as Meissners Latin Phrasebook. The Latin influence in English has been significant at all stages of its insular development. From the 16th to the 18th centuries, English writers cobbled together huge numbers of new words from Latin and Greek words, dubbed inkhorn terms, as if they had spilled from a pot of ink. Many of these words were used once by the author and then forgotten, many of the most common polysyllabic English words are of Latin origin through the medium of Old French. Romance words make respectively 59%, 20% and 14% of English, German and those figures can rise dramatically when only non-compound and non-derived words are included. Accordingly, Romance words make roughly 35% of the vocabulary of Dutch, Roman engineering had the same effect on scientific terminology as a whole
5.
Troposphere
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The troposphere is the lowest portion of Earths atmosphere, and is also where nearly all weather takes place. It contains approximately 75% of the mass and 99% of the total mass of water vapor. The average depths of the troposphere are 20 km in the tropics,17 km in the mid latitudes, the lowest part of the troposphere, where friction with the Earths surface influences air flow, is the planetary boundary layer. This layer is typically a few hundred meters to 2 km deep depending on the landform, atop the troposphere is the tropopause, which is the border between the troposphere and stratosphere. The tropopause is a layer, where the air temperature ceases to decrease with height. Most of the phenomena we associate with day-to-day weather occur in the troposphere, by volume, dry air contains 78. 09% nitrogen,20. 95% oxygen,0. 93% argon,0. 04% carbon dioxide, and small amounts of other gases. Air also contains an amount of water vapor. The chemical composition of the troposphere is essentially uniform, with the exception of water vapor. The source of vapor is at the surface through the processes of evaporation. Thus the proportion of water vapor is normally greatest near the surface, the pressure of the atmosphere is maximum at sea level and decreases with altitude. This is because the atmosphere is nearly in hydrostatic equilibrium. The temperature of the troposphere generally decreases as altitude increases, the rate at which the temperature decreases, − d T / d z, is called the environmental lapse rate. The ELR is nothing more than the difference in temperature between the surface and the tropopause divided by the height. The reason for this difference is that the ground absorbs most of the suns energy. Meanwhile, the radiation of heat at the top of the results in the cooling of that part of the atmosphere. The ELR assumes the atmosphere is still, but as air is heated it becomes buoyant, when a parcel of air rises, it expands, because the pressure is lower at higher altitudes. As the air expands, it pushes the surrounding air outward. As energy transfer to a parcel of air by way of heat is very slow, such a process is called an adiabatic process
6.
Lens (optics)
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A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a piece of transparent material, while a compound lens consists of several simple lenses. Lenses are made from such as glass or plastic, and are ground. A lens can focus light to form an image, unlike a prism, devices that similarly focus or disperse waves and radiation other than visible light are also called lenses, such as microwave lenses, electron lenses, acoustic lenses, or explosive lenses. The word lens comes from the Latin name of the lentil, the genus of the lentil plant is Lens, and the most commonly eaten species is Lens culinaris. The lentil plant also gives its name to a geometric figure, the variant spelling lense is sometimes seen. While it is listed as a spelling in some dictionaries. The oldest lens artifact is the Nimrud lens, dating back 2700 years to ancient Assyria, david Brewster proposed that it may have been used as a magnifying glass, or as a burning-glass to start fires by concentrating sunlight. Another early reference to magnification dates back to ancient Egyptian hieroglyphs in the 8th century BC, the earliest written records of lenses date to Ancient Greece, with Aristophanes play The Clouds mentioning a burning-glass. Some scholars argue that the evidence indicates that there was widespread use of lenses in antiquity. Such lenses were used by artisans for fine work, and for authenticating seal impressions, both Pliny and Seneca the Younger described the magnifying effect of a glass globe filled with water. The Viking lenses were capable of concentrating enough sunlight to ignite fires, between the 11th and 13th century reading stones were invented. Often used by monks to assist in illuminating manuscripts, these were primitive plano-convex lenses initially made by cutting a sphere in half. As the stones were experimented with, it was understood that shallower lenses magnified more effectively. Lenses came into use in Europe with the invention of spectacles. Spectacle makers created improved types of lenses for the correction of vision based more on knowledge gained from observing the effects of the lenses. With the invention of the telescope and microscope there was a deal of experimentation with lens shapes in the 17th. Opticians tried to construct lenses of varying forms of curvature, wrongly assuming errors arose from defects in the figure of their surfaces
7.
Altocumulus cloud
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However, if the layers become tufted in appearance due to increased airmass instability, then the altocumulus clouds become more purely cumuliform in structure. Like other cumuliform and stratocumuliform clouds, altocumulus signifies convection, Altocumulus is also commonly found between the warm and cold fronts in a depression, although this is often hidden by lower clouds. It is therefore one of three warning clouds often recorded by the industry, the other two being towering cumulus and cumulonimbus. Extensive altocumulus formations, particularly if they take the form of undulatus are often referred to as altocumulus mackerel sky, the stratiformis species is composed of sheets or relatively flat patches of stratocumuliform cloud. The synoptic coding is determined by the predominant variety or occasionally by the mother cloud. Altocumulus lenticularis is a middle cloud which can resemble flying saucers. This is formed by uplift associated with mountains. But usually with at least some grey shading and it is coded CM4 on the SYNOP weather observation. Grey shading is also seen with altocumulus castellanus, a middle cloud that can achieve significant vertical development. It is nevertheless usually classified as middle rather than vertical and is coded CM8, the floccus species is a tufted middle cloud which is also associated with greater instability. It shares the same code CM8, chaotic altocumulus, which is typically poorly defined with multiple species or transitional forms arranged in several layers, is coded CM9. Opacity-based varieties, Altocumulus stratiformis has three opacity-based varieties, Translucidus, perlucidus, and opacus, varieties based on opacity are not commonly associatied with the species lenticularis, castellanus, or floccus. Pattern-based varieties, Radiatus is sometimes seen with the stratformis and castellanus species, Altocumulus stratiformis radiatus of any opacity is coded CM5 if it is increasing in amount. The duplicatus or undulatus varieties are seen with the stratiformis and lenticularis species. Altocumulus stratiformis duplicatus is coded CM7 if it is not overridden by another coding of higher importance, lacunosus is very occasionally associated with altocumulus of the species stratiformis, castellanus, or floccus. Precipitation-based supplementary feature, Altocumulus often produces virga but usually not precipitation that reaches the ground, cloud-based supplementary feature, Mamma caused by localized downdrafts in the cloud layer are occasionally seen with altocumulus. Mutatus mother clouds, Altocumulus can form due to the transformation of cirrocumulus, altostratus, nimbostratus. There may be another rare type of altocumulus, altocumulus undulatus asperatus, but this has not been officially named yet
8.
Unidentified flying object
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An unidentified flying object, or UFO, in its most general definition, is any apparent anomaly in the sky that is not identifiable as a known object or phenomenon. Culturally, UFOs are associated with claims of visitation by extraterrestrial life or government-related conspiracy theories, UFOs are often identified after their sighting. Sometimes, however, UFOs cannot be identified because of the low quality of evidence related to their sightings, during the late 1940s and through the 1950s, UFOs were often referred to popularly as flying saucers or flying discs. The term UFO became more widespread during the 1950s, at first in technical literature, UFOs garnered considerable interest during the Cold War, an era associated with a heightened concern for national security. Various studies have concluded that the phenomenon does not represent a threat to national security nor does it contain anything worthy of scientific pursuit, the Oxford English Dictionary defines a UFO as An unidentified flying object, a flying saucer. The first published book to use the word was authored by Donald E. Keyhoe, the acronym UFO was coined by Captain Edward J. Ruppelt, who headed Project Blue Book, then the USAFs official investigation of UFOs. He wrote, Obviously the term flying saucer is misleading when applied to objects of every conceivable shape, for this reason the military prefers the more general, if less colorful, name, unidentified flying objects. Other phrases that were used officially and that predate the UFO acronym include flying flapjack, flying disc, unexplained flying discs, unidentifiable object, the phrase flying saucer had gained widespread attention after the summer of 1947. On June 24, a pilot named Kenneth Arnold reported seeing nine objects flying in formation near Mount Rainier. Arnold timed the sighting and estimated the speed of discs to be over 1,200 mph, at the time, he claimed he described the objects flying in a saucer-like fashion, leading to newspaper accounts of flying saucers and flying discs. In popular usage, the term UFO came to be used to refer to claims of alien spacecraft, between 5% and 20% of reported sightings are not explained, and therefore can be classified as unidentified in the strictest sense. The term Ufology is used to describe the efforts of those who study reports. UFOs have become a prevalent theme in culture, and the social phenomena have been the subject of academic research in sociology and psychology. Unexplained aerial observations have been reported throughout history, an example is Halleys Comet, which was recorded first by Chinese astronomers in 240 BC and possibly as early as 467 BC. Such sightings throughout history often were treated as supernatural portents, angels, or other religious omens. On January 25,1878, the Denison Daily News printed an article in which John Martin, Martin, according to the newspaper account, said it appeared to be about the size of a saucer, the first known use of the word saucer in association with a UFO. In April 1897, thousands of people reported seeing airships in various parts of the United States, scores of people even reported talking to the pilots. Thomas Edison was asked his opinion, and said, You can take it from me that it is a pure fake, the largest had an apparent size of about six Suns, he said
9.
Earth
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Earth, otherwise known as the World, or the Globe, is the third planet from the Sun and the only object in the Universe known to harbor life. It is the densest planet in the Solar System and the largest of the four terrestrial planets, according to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago. Earths gravity interacts with objects in space, especially the Sun. During one orbit around the Sun, Earth rotates about its axis over 365 times, thus, Earths axis of rotation is tilted, producing seasonal variations on the planets surface. The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earths orientation on its axis, Earths lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earths surface is covered with water, mostly by its oceans, the remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earths polar regions are covered in ice, including the Antarctic ice sheet, Earths interior remains active with a solid iron inner core, a liquid outer core that generates the Earths magnetic field, and a convecting mantle that drives plate tectonics. Within the first billion years of Earths history, life appeared in the oceans and began to affect the Earths atmosphere and surface, some geological evidence indicates that life may have arisen as much as 4.1 billion years ago. Since then, the combination of Earths distance from the Sun, physical properties, in the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species that lived on Earth are extinct. Estimates of the number of species on Earth today vary widely, over 7.4 billion humans live on Earth and depend on its biosphere and minerals for their survival. Humans have developed diverse societies and cultures, politically, the world has about 200 sovereign states, the modern English word Earth developed from a wide variety of Middle English forms, which derived from an Old English noun most often spelled eorðe. It has cognates in every Germanic language, and their proto-Germanic root has been reconstructed as *erþō, originally, earth was written in lowercase, and from early Middle English, its definite sense as the globe was expressed as the earth. By early Modern English, many nouns were capitalized, and the became the Earth. More recently, the name is simply given as Earth. House styles now vary, Oxford spelling recognizes the lowercase form as the most common, another convention capitalizes Earth when appearing as a name but writes it in lowercase when preceded by the. It almost always appears in lowercase in colloquial expressions such as what on earth are you doing, the oldest material found in the Solar System is dated to 4. 5672±0.0006 billion years ago. By 4. 54±0.04 Gya the primordial Earth had formed, the formation and evolution of Solar System bodies occurred along with the Sun
10.
Mountain
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A mountain is a large landform that stretches above the surrounding land in a limited area, usually in the form of a peak. A mountain is steeper than a hill. Mountains are formed through tectonic forces or volcanism and these forces can locally raise the surface of the earth. Mountains erode slowly through the action of rivers, weather conditions, a few mountains are isolated summits, but most occur in huge mountain ranges. High elevations on mountains produce colder climates than at sea level and these colder climates strongly affect the ecosystems of mountains, different elevations have different plants and animals. Because of the less hospitable terrain and climate, mountains tend to be used less for agriculture and more for resource extraction and recreation, the highest mountain on Earth is Mount Everest in the Himalayas of Asia, whose summit is 8,850 m above mean sea level. The highest known mountain on any planet in the Solar System is Olympus Mons on Mars at 21,171 m, there is no universally accepted definition of a mountain. Elevation, volume, relief, steepness, spacing and continuity have been used as criteria for defining a mountain, whether a landform is called a mountain may depend on local usage. The highest point in San Francisco, California, is called Mount Davidson, notwithstanding its height of 300 m, similarly, Mount Scott outside Lawton, Oklahoma is only 251 m from its base to its highest point. Whittows Dictionary of Physical Geography states Some authorities regard eminences above 600 metres as mountains, in addition, some definitions also include a topographical prominence requirement, typically 100 or 500 feet. For a while, the US defined a mountain as being 1,000 feet or taller, any similar landform lower than this height was considered a hill. However, today, the United States Geological Survey concludes that these terms do not have technical definitions in the US, using these definitions, mountains cover 33% of Eurasia, 19% of South America, 24% of North America, and 14% of Africa. As a whole, 24% of the Earths land mass is mountainous, there are three main types of mountains, volcanic, fold, and block. All three types are formed from plate tectonics, when portions of the Earths crust move, crumple, compressional forces, isostatic uplift and intrusion of igneous matter forces surface rock upward, creating a landform higher than the surrounding features. The height of the feature makes it either a hill or, if higher and steeper, major mountains tend to occur in long linear arcs, indicating tectonic plate boundaries and activity. Volcanoes are formed when a plate is pushed below another plate, at a depth of around 100 km, melting occurs in rock above the slab, and forms magma that reaches the surface. When the magma reaches the surface, it builds a volcanic mountain. Examples of volcanoes include Mount Fuji in Japan and Mount Pinatubo in the Philippines, the magma does not have to reach the surface in order to create a mountain, magma that solidifies below ground can still form dome mountains, such as Navajo Mountain in the US
11.
Lee wave
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In meteorology, lee waves are atmospheric stationary waves. The most common form is mountain waves, which are atmospheric internal gravity waves and these were discovered in 1933 by two German glider pilots, Hans Deutschmann and Wolf Hirth, above the Krkonoše. They can also be caused by the wind blowing over an escarpment or plateau. The vertical motion forces periodic changes in speed and direction of the air within this air current and they always occur in groups on the lee side of the terrain that triggers them. Usually a turbulent vortex, with its axis of rotation parallel to the range, is generated around the first trough. The strongest lee waves are produced when the lapse rate shows a layer above the obstruction, with an unstable layer above. Lee waves are a form of gravity waves produced when stably stratified flow is forced over an obstacle. This disturbance elevates air parcels above their level of neutral buoyancy, oscillations tilted off the vertical axis at an angle of ϕ will occur at a lower frequency of N cos ϕ. These air parcel oscillations occur in concert, parallel to the wave fronts and these wave fronts represent extrema in the perturbed pressure field, while the areas between wave fronts represent extrema in the perturbed buoyancy field. Energy is transmitted along the fronts, which is the direction of the wave group velocity. In contrast, the propagation of the waves points perpendicular to energy transmission. Waves may also form in dry air without cloud markers, Wave clouds do not move downwind as clouds usually do, but remain fixed in position relative to the obstruction that forms them. Around the crest of the wave, adiabatic expansion cooling can form a cloud in shape of a lens, multiple lenticular clouds can be stacked on top of each other if there are alternating layers of relatively dry and moist air aloft. The rotor may generate cumulus or cumulus fractus in its upwelling portion, the rotor cloud looks like a line of cumulus. It forms on the lee side and parallel to the ridge line and its base is near the height of the mountain peak, though the top can extend well above the peak and can merge with the lenticular clouds above. Rotor clouds have ragged edges and are dangerously turbulent. A foehn wall cloud may exist at the lee side of the mountains, a pileus or cap cloud, similar to a lenticular cloud, may form above the mountain or cumulus cloud generating the wave. Adiabatic compression heating in the trough of each wave oscillation may also evaporate cumulus or stratus clouds in the airmass, lee waves provide a possibility for gliders to gain altitude or fly long distances when soaring
12.
Windward and leeward
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Windward is the direction upwind from the point of reference. Leeward is the direction downwind from the point of reference, the side of a ship that is towards the leeward is its lee side. If the vessel is heeling under the pressure of the wind, during the age of sail, the term weather was used as a synonym for windward in some contexts, as in the weather gage. Windward and leeward directions are important factors to consider when sailing a sailing ship, other terms with broadly the same meaning are widely used, particularly upwind and downwind. The windward vessel is normally the more maneuverable vessel, for this reason, rule 12 of the International Regulations for Preventing Collisions at Sea stipulates that the windward vessel gives way to the leeward vessel. The opposing warship to leeward could often do little but comply without exposing itself unduly and this was particularly important once artillery was introduced to naval warfare. The ships heeled away from the wind so that the vessel was exposing part of her bottom to shot. Leeward and windward refer respectively to what a game stalker would call downwind and upwind, the terms are used by seamen in relation to their ships but also in reference to islands in an archipelago and to the different sides of a single island. In the latter case, the side is that side of an island subject to the prevailing wind. The leeward side is the side protected by the elevation of the island from the prevailing wind, thus, leeward or windward siting is an important weather and climate factor on oceanic islands. In the case of an archipelago, windward islands are upwind and leeward islands are the downwind ones
13.
Dew point
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Dew point is the temperature to which air must be cooled to become saturated with water vapor. When further cooled, the water vapor will condense to form liquid dew. Dew point is called frost point when the temperature is below freezing. The measurement of dew point is related to humidity, a higher dew point means there will be more moisture in the air. Given that all the factors influencing humidity remain constant, at ground level the relative humidity rises as the temperature falls. This is because water vapor condenses as the temperature falls. Dew point temperature is never greater than the air temperature because relative humidity cannot exceed 100%. In technical terms, the dew point is the temperature at which the vapor in a sample of air at constant barometric pressure condenses into liquid water at the same rate at which it evaporates. At temperatures below the dew point, the rate of condensation will be greater than that of evaporation, the condensed water is called dew when it forms on a solid surface. The condensed water is called either fog or a cloud, depending on its altitude, a high relative humidity implies that the dew point is closer to the current air temperature. Relative humidity of 100% indicates the dew point is equal to the current temperature, when the moisture content remains constant and temperature increases, relative humidity decreases. General aviation pilots use dew point data to calculate the likelihood of carburetor icing and fog, at a given temperature but independent of barometric pressure, the dew point is a consequence of the absolute humidity, the mass of water per unit volume of air. If both the temperature and pressure rise, however, the dew point will increase and the humidity will decrease accordingly. Reducing the absolute humidity without changing other variables will bring the dew point back down to its initial value, in the same way, increasing the absolute humidity after a temperature drop brings the dew point back down to its initial level. If the temperature rises in conditions of constant pressure, then the dew point will remain constant but the relative humidity will drop. For this reason, a constant relative humidity with different temperatures implies that when it is hotter, a higher fraction of the air is present as water vapor compared to when it is cooler. At a given barometric pressure but independent of temperature, the dew point indicates the fraction of water vapor in the air, or, put differently. If the pressure rises without changing this mole fraction, the dew point will rise accordingly, reducing the mole fraction, i. e. making the air less humid, would bring the dew point back down to its initial value
14.
Wave cloud
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A wave cloud is a cloud form created by atmospheric internal waves. As an air mass travels through the wave, it undergoes repeated uplift, 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 heating, leading to the characteristic clouded. The cloud base on the side is higher than on the windward side. It is possible that simple convection from mountain summits can also form wave clouds and this occurs as the convection forces a wave or lenticular wave cloud into the more stable air above. Wave clouds are typically mid- to upper-tropospheric ice clouds and they are relatively easy to study, because they are quite consistent. As a result, they are being analyzed to increase our understanding of how these upper-level ice clouds influence the Earths radiation budget, understanding this can improve climate models. The streamlines in these clouds have the steepest slope a few kilometers downwind of the lee slope of a mountain and it is in these regions of highest vertical velocity that sailplanes can reach record-breaking altitudes. Wave cloud structure ranges from smooth and simple, to jumbled phases occurring randomly, often, ice crystals can be found downwind of the waves. Whether this happens depends on the saturation of the air, the composition of the ice is currently an active topic of study. The main mechanism for ice formation is homogeneous nucleation, the ice crystals are mostly small spheroidal and irregular-shaped particles. Ice columns make up less than 1%, and plates are virtually nonexistent, multi-level mountain wave clouds form when the moisture in the air above the mountain is located in distinct layers, and vertical mixing is inhibited
15.
Cloud iridescence
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Cloud iridescence is the occurrence of colors in a cloud similar to those seen in oil films on puddles, located in the general vicinity of the sun or moon. It is a common phenomenon, most often observed in altocumulus, cirrocumulus, lenticular clouds. The colors are usually pastel, but can be very vivid, when occurring near the sun, the effect can be difficult to spot as it is drowned in the suns glare. This may be overcome by blocking the sun with ones 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. The effect is similar to irisation, Iridescent clouds are a diffraction phenomenon caused by small water droplets or small ice crystals individually scattering light. Larger ice crystals do not produce iridescence, but can cause halos, if parts of clouds contain small water droplets or ice crystals of similar size, their cumulative effect is seen as colors. The cloud must be thin, so that most rays encounter only a single droplet. Iridescence is therefore mostly seen at cloud edges or in semi-transparent clouds, polar stratospheric cloud Iridescent cloud gallery - Atmospheric Optics site On the Cause of Iridescence in Clouds - Scientific American Supplement
16.
Gliding
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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 phenomena have allowed greater distances at higher average speeds. Long distances are now flown using any of the sources of rising air, ridge lift, thermals. When conditions are favourable, experienced pilots can now fly hundreds of kilometres before returning to their home airfields, some competitive pilots fly in races around pre-defined courses. These gliding competitions test pilots abilities to make best use of weather conditions as well as their flying skills. Local and national competitions are organized in countries, and there are biennial World Gliding Championships. Techniques to maximize a gliders speed around the task in a competition have been developed, including the optimum speed to fly, navigation using GPS. If the weather deteriorates pilots are unable to complete a cross-country flight. Consequently, they may need to land elsewhere, perhaps in a field, powered-aircraft and winches are the two most common means of launching gliders. These and other methods require assistance and facilities such as airfields, tugs. These are usually provided by gliding clubs who also train new pilots, the development of heavier-than-air flight in the half century between Sir George Cayleys coachman in 1853 and the Wright brothers in 1903 mainly involved gliders. With the active support of the German government, there were 50,000 glider pilots by 1937, the first German gliding competition was held at the Wasserkuppe in 1920, organized by Oskar Ursinus. The best flight lasted two minutes and set a distance record of 2 kilometres. Within ten years, it had become an event in which the achieved durations. In 1931, Gunther Grönhoff flew 272 kilometres on the front of a storm from Munich to Kadaň in Western Czechoslovakia, in the 1930s, gliding spread to many other countries. In the 1936 Summer Olympics in Berlin gliding was a demonstration sport, a glider, the Olympia, was developed in Germany for the event, but World War II intervened. By 1939 the major gliding records were held by Russians, including a record of 748 kilometres
17.
Glider (sailplane)
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A sailplane or glider is a type of glider aircraft used in the sport of gliding. Sailplanes are aerodynamically streamlined and are capable of soaring in rising air, sailplanes benefit from producing the least drag for any given amount of lift, and this is best achieved with long, thin wings, a fully faired narrow cockpit and a slender fuselage. Aircraft with these features are able to climb efficiently in rising air produced by thermals or hills, sailplanes can glide long distances at high speed with a minimum loss of height in between. Gliders have rigid wings and either skids or undercarriage, in contrast hang gliders and paragliders use the pilots feet for the start of the launch and for the landing. These latter types are described in articles, though their differences from sailplanes are covered below. Gliders are usually launched by winch or aerotow, though other methods, auto tow, all sailplanes soar, but some gliders do not soar and are simply engineless aircraft towed by another aircraft to a desired destination and then cast off for landing. Military gliders are only, and are abandoned after landing, having served their purpose. Motor gliders are gliders with engines which can be used for extending a flight and even, in some cases, Some high-performance motor gliders may have an engine-driven retractable propeller which can be used to sustain flight. Other motor gliders have enough thrust to launch themselves before the engine is retracted and are known as self-launching gliders, another type is the self-launching touring motor glider, where the pilot can switch the engine on and off in flight without retracting their propellers. Sir George Cayleys gliders achieved brief wing-borne hops from around 1849, in the 1890s Otto Lilienthal built gliders using weight shift for control. In the early 1900s the Wright Brothers built gliders using movable surfaces for control, in 1903 they successfully added an engine. After World War I gliders were built for sporting purposes in Germany, the sporting use of gliders rapidly evolved in the 1930s and is now their main application. As their performance improved, gliders began to be used for cross-country flying, in 1930, pilot Frank Hawks flew the Texaco Eaglet with tow plane from San Diego to New York over eight days, helping to popularize the activity in the United States. Early gliders had no cockpit and the pilot sat on a seat located just ahead of the wing. These were known as gliders and they were usually launched from the tops of hills. To enable gliders to soar more effectively than primary gliders, the designs minimized drag, gliders now have very smooth, narrow fuselages and very long, narrow wings with a high aspect ratio and winglets. The early gliders were mainly of wood with metal fastenings, stays. Later fuselages made of fabric-covered steel tube were married to wood and fabric wings for lightness, New materials such as carbon-fiber, fiber glass and Kevlar have since been used with computer-aided design to increase performance
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Pileus (meteorology)
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Pilei tend to change shape rapidly. They are formed by strong updraft at lower altitudes, acting upon moist air above, clouds that are attached to pilei are often given the suffix pileus or with pileus. For example, a cloud with a pileus attached to it would be called cumulonimbus with pileus. Pilei can also form above ash clouds and pyrocumulus clouds from erupting volcanoes, pilei form above some mushroom clouds of high-yield nuclear detonations. A sheet of altostratus cloud often is seen lower down in a cumulonimbus cloud, pilei clouds indicate that the parent cloud is growing rapidly, has plenty of moisture, and is highly unstable. This means that the parent cloud could quickly grow to become a cumulonimbus cloud and these clouds can cause severe weather and sightings of pilei should be viewed as a warning of an impending storm. Pilei also indicate strong and possibly damaging winds, atmospheric convection Lenticular cloud Helm Wind Video – Video of pileus clouds
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Noctilucent cloud
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Night clouds or noctilucent clouds are tenuous cloud-like phenomena in the upper atmosphere. They are visible in a deep twilight and they are made of ice crystals. Noctilucent roughly means night shining in Latin and they are most commonly observed in the summer months at latitudes between 50° and 70° north and south of the equator. These clouds can be observed only during summer months and when the Sun is below the horizon for the observer. They are the highest clouds in Earths atmosphere, located in the mesosphere at altitudes of around 76 to 85 kilometres. They are too faint to be seen during daylight, and are visible only when illuminated by sunlight from below the horizon while the lower layers of the atmosphere are in the Earths shadow. Noctilucent clouds can form only under restricted conditions during local summer. They are a recent classification. The occurrence of noctilucent clouds appears to be increasing in frequency, brightness and extent. Night clouds or noctilucent clouds are composed of crystals of water ice up to 100 nm in diameter and exist at a height of about 76 to 85 km. Clouds in the Earths lower atmosphere form when water collects on particles, data from the Aeronomy of Ice in the Mesosphere satellite suggests that noctilucent clouds require water vapour, dust, and very cold temperatures to form. The sources of both the dust and the vapour in the upper atmosphere are not known with certainty. The dust is believed to come from micrometeors, although particulates from volcanoes, the moisture could be lifted through gaps in the tropopause, as well as forming from the reaction of methane with hydroxyl radicals in the stratosphere. About half of the vapour was released into the thermosphere, usually at altitudes of 103 to 114 km, in August 2014, a SpaceX Falcon 9 also caused noctilucent clouds over Orlando, FL after a launch. The exhaust can be transported to the Arctic region in little over a day, as the water migrates northward, it falls from the thermosphere down into the colder mesosphere, which occupies the region of the atmosphere just below. Although this mechanism is the cause of individual noctilucent clouds, it is not thought to be a contributor to the phenomenon as a whole. Noctilucent clouds form mostly near the regions, because the mesosphere is coldest there. Clouds in the southern hemisphere are about 1 km higher than those in the northern hemisphere, ultraviolet radiation from the Sun breaks water molecules apart, reducing the amount of water available to form noctilucent clouds
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Polar stratospheric cloud
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Polar stratospheric clouds or PSCs, also known as nacreous clouds, are clouds in the winter polar stratosphere at altitudes of 15, 000–25,000 meters. They are best observed during civil twilight when the sun is between 1 and 6 degrees below the horizon as well as in winter and in northerly latitudes. They are implicated in the formation of ozone holes, the stratosphere is very dry, unlike the troposphere, it rarely allows clouds to form. In the extreme cold of the winter, however, stratospheric clouds of different types may form. PSCs form at low temperatures, below −78 °C. These temperatures can occur in the stratosphere in polar winter. In the Antarctic, temperatures below −88 °C frequently cause type II PSCs, such low temperatures are rarer in the Arctic. In the Northern hemisphere, the generation of lee waves by mountains may locally cool the lower stratosphere, forward-scattering of sunlight within the clouds produces a pearly-white appearance. Particles within the optically thin clouds cause colored Interference fringes by diffraction, the visibility of the colors may be enhanced with a polarising filter. PSCs are classified into three types Ia, Ib and II according to their chemical composition which can be measured using LIDAR, the technique also determines the height and ambient temperature of the cloud. Type Ib clouds contain small, spherical particles, of a liquid supercooled ternary solution of acid, nitric acid. Type Ic clouds consist of metastable water-rich nitric acid in a solid phase, Type II clouds, which are very rarely observed in the Arctic, consist of water ice only. Only Type II clouds are necessarily nacreous whereas Type I clouds can be iridescent under certain conditions, just as any other cloud
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Cirrus cloud
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Cirrus is a genus of atmospheric cloud generally characterized by thin, wispy strands, giving the type its name from the Latin word cirrus, meaning a ringlet or curling lock of hair. This cloud can form anywhere between 16,500 and 45,000 feet in the sky, the strands of cloud sometimes appear in tufts of a distinctive form referred to by the common name of mares tails. On planet Earth, cirrus generally appears white or light gray in color and it forms when water vapor undergoes deposition at altitudes above 5,500 m in temperate regions and above 6,400 m in tropical regions. It also forms from the outflow of tropical cyclones or the anvils of cumulonimbus cloud, since cirrus clouds arrive in advance of the frontal system or tropical cyclone, it indicates that weather conditions may soon deteriorate. While it indicates the arrival of precipitation, cirrus clouds only produce fall streaks, jet stream-powered cirrus can grow long enough to stretch across continents while remaining only a few kilometers deep. When visible light interacts with the ice crystals in cirrus cloud, it produces optical phenomena such as sun dogs, Cirrus is known to raise the temperature of the air beneath the main cloud layer by an average of 10 °C. When the individual filaments become so extensive that they are virtually indistinguishable from one another, convection at high altitudes can produce another high-based genus called cirrocumulus, a pattern of small cloud tufts that contain droplets of supercooled water. Cirrus clouds form on planets, including Mars, Jupiter, Saturn, Uranus. They have even seen on Titan, one of Saturns moons. Some of these extraterrestrial cirrus clouds are composed of ammonia or methane ice rather than water ice, the term cirrus is also used for certain interstellar clouds composed of sub-micrometer-sized dust grains. Cirrus cloud ranges in thickness from 100 m to 8,000 m, with an average thickness of 1,500 m. There are, on average,30 ice crystals per liter, but this ranges from one ice crystal per 10,000 liters to 10,000 ice crystals per liter, a difference of eight orders of magnitude. The length of each of these ice crystals is usually 0.25 millimeters long, the ice crystals in contrails are much smaller than those in naturally occurring cirrus cloud, as they are around 0.001 millimeters to 0.1 millimeters in length. Cirrus can vary in temperature from −20 °C to −30 °C, the ice crystals in cirrus clouds have different shapes in addition to different sizes. Some shapes include solid columns, hollow columns, plates, rosettes, the shape of the ice crystals is determined by the air temperature, atmospheric pressure, and ice supersaturation. Cirrus in temperate regions typically have the shapes segregated by type, in the northern Arctic region, cirrus tend to be composed of only the columns, plates, and conglomerations, and these crystals tend to be at least four times larger than the minimum size. In Antarctica, cirrus are usually composed of only the columns, scientists have studied the characteristics of cirrus using several different methods. One, Light Detection and Ranging, gives highly accurate information on the altitude, length
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Cirrostratus cloud
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Cirrostratus /ˌsɪroʊˈstrɑːtəs/ is a high, very thin, generally uniform stratiform genus-type of cloud, composed of ice-crystals. It is difficult to detect and is capable of forming halos when the cloud takes the form of thin cirrostratus nebulosus, the cloud has a fibrous texture with no halos if it is thicker cirrostratus fibratus. On the approach of a system, the cirrostratus often begins as nebulosus. If the cirrostratus begins as fragmented fibratus it often means the front is weak, Cirrostratus is usually located above 5.5 km. Its presence indicates a large amount of moisture in the upper atmosphere, if the cirrostratus is broken fibratus it can mean that the front is weak and that stratus rather than nimbostratus will be the precipitating cloud. Contrails also tend to spread out and can be visible for up to an hour in cirrostratus, the phrase milky sunshine is often, as well as referring to haze or light mist, used to refer to the milky look of the sky when cirrostratus is present. Species, Cirrostratus fibratus is a fibrous sheet similar to cirrus. It is reported in the SYNOP code as CH8 or as CH5 or 6 if increasing in amount, if the high cloud covers the entire sky and takes on the form of a featureless veil, it is classified as cirrostratus of the species nebulosus and is coded CH7. Varieties, Cirrostratus species have no opacity-based varieties as they are always translucent, two pattern-based varieties are sometimes seen with the species fibratus. These are the closely spaced duplicatus and wavy undulatus types similar to those seen with cirrus fibratus, pattern-based varieties are not commonly associated with the species nebulosus due to its lack of features. Supplementary features, Cirrostratus produces no precipitation or virga, and is not accompanied by any accessory clouds, genitus mother clouds, Cirrostratus fibratus cirrocumulogenitus sometimes appears as the latter cloud flattens and loses some of its stratocumuliform structure. Cirrostratus fibratus cumulonimbogenitus may form if the top of a mature thundercloud spreads. Mutatus mother clouds, Cirrostratus fibratus cirromutatus or cirrocumulomutatus are the result of a transformation from cirrus and cirrocumulus genus types. Cirrostratus nebulosis altostratomutatus results when a high grey nebulous altostratus layer thins out into a layer of featureless high cloud. Stratus cloud Altostratus cloud Nimbostratus cloud Cirrostratus nebulosus Altostratus undulatus cloud Fractus cloud International Cloud Atlas – Cirrostratus
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Cirrocumulus cloud
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Cirrocumulus is one of the three main genus-types of high-altitude tropospheric clouds, the other two being cirrus and cirrostratus. They usually occur at an altitude of 5 kilometres to 12 kilometres, like lower altitude cumuliform and stratocumuliform clouds, cirrocumulus signifies convection. Unlike other high cirrus and cirrostratus, cirrocumulus includes an amount of liquid water droplets. Ice crystals are the predominant component, and typically, the ice crystals cause the water drops in the cloud to rapidly freeze. This process can produce precipitation in the form of a virga consisting of ice or snow. Thus cirrocumulus clouds are usually short-lived and they usually only form as part of a short-lived transitional phase within an area of cirrus clouds and can also form briefly as a result of the breaking up of part of a cumulonimbus anvil. Properly, the term refers to each cloud, but is typically also used to refer to an entire patch of cirrocumulus. When used in way, each cirrocumulus element is referred to as a cloudlet. Each cloudlet appears no larger than a finger held at arms length, Cirrocumulus is coded CH9 for the main genus-type and all subforms. Cirrocumulus is distinguished from altocumulus in several ways, although the two stratocumuliform genus types can occur together with no clear demarcation between them. Cirrocumulus generally occur at higher altitudes than altocumulus, and thus the cloudlets appear smaller as they are distant from observation at ground level. Cirrocumulus clouds never cast self-shadows and are translucent to a certain degree and they are also typically found amongst other cirrus clouds in the sky, and are usually themselves seen to be transforming into these other types of cirrus. This often occurs at the edge of a warm front. Cirrocumulus clouds tend to reflect the red and yellow colours during a sunset and sunrise, if it forms in patches with cirrus or cirrostratus and the clouds spread across the sky, it usually means rain in 8–10 hours. If there are small patches of cirrocumulus and perhaps some wisps of cirrus. If it is seen after rain it usually means improving weather, species, Cirrocumulus stratiformis is one of four species and appears in the form of relatively flat stratocumuliform sheets or patches. The species lenticularis takes its name from the structure of this cloud which is tapered at each end. Cirrocumulus castellanus has cumuliform buildups that give the cloud a partly or mainly turreted appearance, when the cumuliform parts have more of a tufted appearance, it is given the species name floccus
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Contrail
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Contrails are line-shaped clouds sometimes produced by aircraft engine exhaust, typically at aircraft cruise altitudes several miles above the Earths surface. Contrails are composed primarily of water, in the form of ice crystals, the combination of water vapor in aircraft engine exhaust and the low ambient temperatures that often exist at these high altitudes allows the formation of the trails. Their formation can also be triggered by changes in air pressure in wingtip vortices or in the air over the wing surface. Contrails, and other clouds directly resulting from human activity, are collectively named homogenitus, persistent contrails are of particular interest to scientists because they increase the cloudiness of the atmosphere. The resulting cloud forms are described as homomutatus, and may resemble cirrus, cirrocumulus, or cirrostratus. Persistent spreading contrails are suspected to have an effect on global climate, the main products of hydrocarbon fuel combustion are carbon dioxide and water vapor. At high altitudes this water vapor emerges into an environment. The vapor then condenses into water droplets which freeze if the temperature is low enough. These millions of tiny water droplets and/or ice crystals form the contrails, the time taken for the vapor to cool enough to condense accounts for the contrail forming some distance behind the aircraft. At high altitudes, supercooled water vapor requires a trigger to encourage deposition or condensation, the exhaust particles in the aircrafts exhaust act as this trigger, causing the trapped vapor to condense rapidly. Exhaust contrails usually form at altitudes, usually above 8,000 m. They can also form closer to the ground when the air is cold, a 2013-2014 study jointly hosted by NASA, German aerospace center DLR, and Canadas National Research Council NRC, determined that biofuels could reduce contrail generation. This reduction was explained by demonstrating that biofuels produce fewer soot particles, the tests were performed by flying a DC-8 at cruising altitude with a sample-gathering aircraft flying in trail. In these samples, the contrail-producing soot particle count was reduced by 50 to 70 percent, using a 50% blend of conventional Jet A1 fuel and HEFA biofuel produced from camelina. As a wing generates lift, it causes a vortex to form at the wingtip, the reduction in pressure and temperature across each vortex can cause water to condense and make the cores of the wingtip vortices visible. This effect is common on humid days. Wingtip vortices can sometimes be seen behind the wing flaps of airliners during takeoff and landing, the visible cores of wingtip vortices contrast with the other major type of contrails which are caused by the combustion of fuel. Contrails produced from jet engine exhaust are seen at high altitude and they trail behind the wingtips and wing flaps rather than behind the engines
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Altostratus cloud
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Altostratus is a middle altitude cloud genus belonging to the stratiform physical category characterized by a generally uniform gray to bluish-green and sheet or layer. It is lighter in color than nimbostratus and darker than high cirrostratus, the sun can be seen through thin altostratus, but thicker layers can be quite opaque. Altostratus is formed by the lifting of a mostly stable air mass that causes invisible water vapor to condense into cloud. It can produce light precipitation, often in the form of virga, if the precipitation increases in persistence and intensity, the altostratus cloud may thicken into nimbostratus. Altostratus most often takes the form of a sheet of cloud. It can also be fragmented with clear sky visible, which signals the approach of a weakened or upper level warm front. Altostratus may be composed of ice crystals, in some ice crystal altostratus, very thin, rapidly disappearing horizontal sheets of water droplets appear at random. The sizes of the ice crystals in the cloud tended to increase as altitude decreased, however, close to the bottom of the cloud, the particles decreased in size again. During the sampling of one cloud, the noted a halo while flying near the top of the cloud. However, farther down, the ice became more conglomerated. Altostratus tends to form ahead of a warm or occluded front, however it can also occur together with cumulus congestus or cumulonimbus at a cold front. Species, Altostratus is not divided into species because it is always nebulous or featureless in structure, opacity-based varieties, Altocumulus translucidus is relatively thin so that the sun or moon is always visible as if seen through frosted glass. It is strictly a middle cloud and is coded CM1 in the SYNOP report, the opacus variety is sufficiently thick to obscure the sun or moon and can extend vertically into the high étage. It is therefore classified as vertical or multi-level, but is still coded CM2 as a middle cloud. Pattern-based varieties, Radiatus, duplicatus, and undulatus are all associated with altostratus. Precipitation-based supplementary features, Altostratus opacus can be enough to produce both virga or praecipitatio features. Cloud-based supplementary feature, Mamma may be seen with altostratus. Accessory cloud, Pannus forming in precipitation is seen with altostratus and is coded CL7
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Altocumulus castellanus cloud
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Altocumulus Castellanus is named for its tower-like projections that billow upwards from the base of the cloud. The base of the cloud can form as low as 2,000 metres, or as high as 6,000 metres and they are very similar to cumulus congestus clouds, but at a higher level. Castellanus clouds are evidence of mid-atmospheric instability and a high mid-altitude lapse rate, Altocumulus Castellanus clouds are typically accompanied by moderate turbulence as well as potential icing conditions. For these reasons, flight through Altocumulus Castellanus clouds is often best avoided by aircraft, the appearance of Altocumulus Castellanus early in a sunny day may indicate a high probability the formation of thunderstorms in the afternoon, as they may develop into cumulonimbus storm clouds
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Stratus cloud
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Stratus clouds are low-level clouds characterized by horizontal layering with a uniform base, as opposed to convective or cumuliform clouds that are formed by rising thermals. More specifically, the term stratus is used to describe flat, hazy, the word stratus comes from the Latin prefix strato-, meaning layer. Stratus clouds may produce a light drizzle or an amount of snow. These clouds are essentially above-ground fog formed either through the lifting of morning fog or through cold air moving at low altitudes over a region, some call these clouds high fog for the fog-like cloud. While light rain may fall, this cloud does not indicate much meteorological activity, Stratus clouds form when a sheet of warm, moist air lifts off the ground and depressurizes, following the lapse rate. This causes the relative humidity to increase due to the adiabatic cooling, Stratus clouds look like featureless gray to white sheets of cloud. They can be composed of droplets, supercooled water droplets. Stratus nebulosus clouds appear as a featureless or nebulous veil or layer of clouds with no distinctive features or structure. They are found at low altitudes, and is a sign of atmospheric stability. Stratus nebulosus may produce light drizzle, or flakes of snow, Stratus fractus clouds on the other hand, appear with an irregular shape, and forms with a clearly fragmented or ragged appearance. They mostly appear under the precipitation of major rain-bearing clouds and these are the nimbostratus clouds, and the cumulonimbus clouds, and are classified as pannus clouds. Stratus fractus can also form beside mountain slopes, without the presence of nimbus clouds, Stratus fractus are not divided into varieties, but stratus nebulosus on the other hand, are divided into two. The Stratus opacus variety appears as a nebulous or milky sheet of the nebulosus species, Stratus Translucidus is another variety of the nebulosus species. These clouds are considered more thin than the opacus variety because this cloud is rather translucent, Stratus clouds only have one pattern-based variety. This is the stratus undulatus variety, mild undulations can be observed from this cloud, only associated by the nebulosus species. Though rare, this formation is caused by disturbances on the gentle wind shear. Stratus undulatus clouds are common on stratus stratocumulomutatus clouds where the wind is stronger as height increases. Stratus cumulogenitus clouds occur when the base of cumulus clouds spreads and this can also occur on nimbostratus clouds and on cumulonimbus clouds
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Stratocumulus cloud
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Weak convective currents create shallow cloud layers because of drier, stable air above preventing continued vertical development. Most often, stratocumulus produce no precipitation, and when they do, however, these clouds are often seen at either the front or tail end of worse weather, so they may indicate storms to come, in the form of thunderheads or gusty winds. Stratocumulus clouds are same in appearance to altocumulus and are mistaken for such. This often does not apply when stratocumulus is of a broken, fractus form, stratocumulus is also often, though not always, darker in colour than altocumulus. Stratocumulus clouds are the type of cloud that can produce crepuscular rays. Thin stratocumulus clouds are often the cause of corona effects around the Moon at night. All stratocumulus subtypes are coded CL5 except when formed from free convective mother clouds or when formed separately from co-existing, stratocumulus Stratiformis are extensive flat but slightly lumpy sheets that show only minimal convective activity. Stratocumulus Lenticularis are separate flat elongated seed-shaped clouds and they are typical for polar countries or warmer climate during winter seasons. They also can be formed by winds passing hills or mountains, such as Foehn winds, stratocumulus Castellanus have stronger convective activity due to the presence of increasingly unstable air. They are distinct from other stratocumulus by puffy tower-like formations atop the cloud layer, stratocumulus castellanus may develop into cumulus congestus under auspicious conditions. Any showers from stratocumulus castellanus are not usually as heavy as those from cumulus congestus, stratocumulus Opacus is a dark layer of clouds covering entire sky without any break. However, the sheet is not completely uniform, so that separate cloud bases still can be seen. This is the main precipitating type, however any rain is usually light, if the cloud layer becomes grayer to the point when individual clouds can’t be distinguished, stratocumulus turn into stratus clouds. Stratocumulus Perlucidus is a layer of clouds with small spaces, appearing in irregular pattern. Stratocumulus Translucidus consist of groups of stratocumulus clouds, with a clear sky visible between them. Stratocumulus Undulatus clouds appear as nearly parallel waves, rolls or separate elongated clouds, stratocumulus Duplicatus clouds appear as stratocumulus clouds with two or more layers or sheets. Stratocumulus duplicatus is common on species lenticularis or lenticular cloud, stratocumulus Lacunosus clouds are very uncommon. They only occur there are localized downdrafts striking through the stratocumuliform cloud
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Cumulus cloud
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Cumulo- means heap or pile in Latin. Cumulus clouds are often described as puffy, cotton-like or fluffy in appearance, Cumulus clouds, being low-level clouds, are generally less than 2,000 m in altitude unless they are the more vertical cumulus congestus form. Cumulus clouds may appear by themselves, in lines, or in clusters, Cumulus clouds are often precursors of other types of cloud, such as cumulonimbus, when influenced by weather factors such as instability, moisture, and temperature gradient. Normally, cumulus clouds produce little or no precipitation, but they can grow into the precipitation-bearing congestus or cumulonimbus clouds, Cumulus clouds can be formed from water vapor, supercooled water droplets, or ice crystals, depending upon the ambient temperature. They come in many distinct subforms, and generally cool the earth by reflecting the solar radiation. Cumulus clouds are part of the category of free-convective cumuliform clouds. The latter genus-type is sometimes categorized separately as cumulonimbiform due to its complex structure that often includes a cirriform or anvil top. There are also cumuliform clouds of limited convection that comprise stratocumulus, altocumulus and cirrocumulus and these last three genus-types are sometimes classified separately as stratocumuliform. Cumulus clouds form via atmospheric convection as air warmed by the surface begins to rise, as the air rises, the temperature drops, causing the relative humidity to rise. If convection reaches a level the RH reaches one hundred percent. At this point a positive feedback ensues, since the RH is above 100%, water condenses, releasing latent heat, warming the air. In this phase, water condenses on various nuclei present in the air. This creates the characteristic flat-bottomed puffy shape associated with cumulus clouds, the height of the cloud depends on the temperature profile of the atmosphere and the presence of any inversions. During the convection, surrounding air is entrained with the thermal, rain forms in a cumulus cloud via a process involving two non-discrete stages. The first stage occurs after the droplets coalesce onto the various nuclei, langmuir writes that surface tension in the water droplets provides a slightly higher pressure on the droplet, raising the vapor pressure by a small amount. The increased pressure results in those droplets evaporating and the water vapor condensing on the larger droplets. In the accretion phase, the raindrop begins to fall, and other droplets collide, langmuir was able to develop a formula which predicted that the droplet radius would grow unboundedly within a discrete time period. The liquid water density within a cumulus cloud has been found to change with height above the base rather than being approximately constant throughout the cloud
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Fractus cloud
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Fractus clouds are small, ragged cloud fragments that are usually found under an ambient cloud base. They form or have broken off from a cloud, and are generally sheared by strong winds. Fractus have irregular patterns, appearing much like torn pieces of cotton candy and they change constantly, often forming and dissipating rapidly. They do not have clearly defined bases, sometimes they are persistent and form very near the surface. Common kinds include scud and cloud tags, fractus are accessory clouds, named for the type of cloud from which they were sheared. The two principal forms are cumulus fractus and stratus fractus, fractus clouds may develop into cumulus if the ground heats enough to start convection. Stratus fractus is distinguishable from cumulus fractus by its vertical extent, darker color. Cumulus fractus clouds actually look like ragged cumulus clouds and they may originate from dissipated cumulus clouds, appearing in this case as white ragged clouds located at significant distances from each other. Cumulus fractus in particular form on the leading and trailing edges of summer storms in warm, observing fractus gives an indication of wind movements under the parent cloud. Masses of multiple fractus clouds, located under a cloud, are called pannus. Fractonimbus are a form of stratus fractus, developing under precipitation clouds due to turbulent air movement and they are dark-gray and ragged in appearance. Fractonimbus exist only under precipitation clouds, and dont produce precipitation themselves, fractonimbus may eventually merge completely with overlying nimbostratus clouds. In rainstorms, scud often form in the area where the air has been cooled by precipitation from the downdraft. If scud are rising and moving towards the main updraft, sometimes marked by a base or wall cloud. In addition to forming in inflow, fractus also form in outflow, scud are very common on the leading edge of a thunderstorm where warm, moist air is lifted by the gust front. Scud are usually found under shelf clouds
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Cumulus humilis cloud
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Cumulus humilis is a cumuliform cloud with little vertical extent that is commonly referred to as fair weather cumulus and common in the summer. Though if they develop into cumulus mediocris cloud or the cumulus congestus cloud it may mean thunderstorms later in the day and it is generally classified as a low cloud, but in hot countries and over mountainous terrain these clouds occur at up to 6,000 m altitude. Elsewhere they are found lower levels. This indicates that the temperature in the atmosphere above them either drops off very slowly or not at all with altitude, in this case, a warm front could be approaching and this means rain is likely in the next 12 to 24 hours. When they appear in a sky, they are an indicator of pleasant weather for the next several hours. Air below the base can be quite turbulent, giving occupants of light aircraft an uncomfortable ride. To avoid turbulence where such clouds are present, pilots may climb above the cloud tops, however, glider pilots actively seek out the rising air to gain altitude. These clouds may later grow to larger cumulus clouds under the right conditions, if these clouds are present in the morning it is a sign of an unstable atmosphere. Larger clouds and possibly thunderstorms could form throughout the day to cause bad or severe weather in the afternoon or evening, Cumulus humilis clouds are not rain clouds but could show an impending storm in the future. They are formed by rising air or thermal that has been heated by the ground. It is a very small convective cloud and form usually only after a thermal reaches dew point. They can also form into cumulus mediocris cloud then can easily dissipate only minutes after formation, Cumulus mediocris Atmospheric convection Cumulus humilis
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Actinoform cloud
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An actinoform or actiniform cloud is a collection of marine low clouds that takes a distinct shape. They are named after the Greek word for ray due to their radial structure, actinoform clouds can spread out over 300 kilometers across and thus cannot be easily seen with the naked eye. In addition, actinoform clouds can form trains that are up to six times the length of the cloud field, yet they maintain their own. In a satellite image, they look like distinct leaf-like or spokes-on-a-wheel patterns that stand out from the rest of the cloud field. Actinoform clouds were discovered in the 1960s soon after the launch of the TIROS V weather satellite, but until the late 1990s, scientists had dismissed them as merely a relatively uncommon transitional form between open- and closed-cell formations of stratocumulus clouds. In fact, the term actinoform is not included in the 2000 edition of the Glossary of Meteorology, however, these clouds are much more prevalent and complex than was originally thought. Such cloud systems are persistent year-round off the coast, yet in certain seasons they blow ashore and these cloud systems rarely form near the equator. The effect of clouds on weather systems and climate patterns is still being analyzed. Meteorology professor Bjorn Stevens of the University of California, Los Angeles theorizes that they, when the open cells are present—and likewise actinoform clouds—there seems to be a corresponding increase in drizzle. Thus, data from recent field studies suggest that the presence of pockets of open cells, in fact, professor Stevens discovered that the shape of the cloud field reorganizes itself when the clouds begin to rain. These clouds have also known to carry hail. Cloudy With a Chance of Drizzle, cloud Formations off the West Coast of South America. Actiniform cloud system in the Southeast Pacific, video at YouTube
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Asperitas (cloud)
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Asperitas is a cloud formation first popularized and proposed as a type of cloud in 2009 by Gavin Pretor-Pinney of the Cloud Appreciation Society. Added to the International Cloud Atlas in March of 2017, it is the first cloud formation added since cirrus intortus in 1951, the name translates approximately as roughness. The clouds are closely related to undulatus clouds, although they appear dark and storm-like, they almost always dissipate without a storm forming. The ominous-looking clouds have been common in the Plains states of the United States. Margaret LeMone, an expert with the National Center for Atmospheric Research has taken photos of asperatus clouds for 30 years, and considers it in her own words. On June 20,2006 Jane Wiggins took a picture of asperatus clouds from the window of an office building in Cedar Rapids. In March 2009, Chad Hedstroom took a picture of asperatus clouds from his car near Greenville Ave in Dallas, Texas, soon after taking it, Wiggins sent her Cedar Rapids image to the Cloud Appreciation Society, which displayed it on its image gallery. Wiggins photograph was posted on the National Geographic website on June 4,2009, on July 23,2013, Janet Salsman photographed them along the South Shore of Nova Scotia, Canada. On October 28,2013, an Asperitas cloud layer formed over Tuscaloosa, on July 7,2014 asperatus clouds in Lincoln, Nebraska, have been caught on tape by Alex Schueth. One of the most dramatic formations was captured by Witta Priester in New Zealand in 2005, the photo was posted by NASA as the Astronomy Picture of the Day and shows great detail, partly because sunlight illuminates the undulating clouds from the side. Media related to Asperitas at Wikimedia Commons
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Nimbostratus cloud
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This change in classification would once have made it a Family D cloud, but this style of nomenclature was discontinued by the WMO in 1956. Nimbostratus usually produces precipitation over a wide area, nimbo- is from the Latin word nimbus, which denotes precipitation. It has a cloud base generally found anywhere from near surface in the low levels. Although usually dark at its base, it often appears illuminated from within to a surface observer, Nimbostratus usually has a thickness of about 2000 m. Though found worldwide, nimbostratus occurs more commonly in the middle latitudes and it is coded CM2 on the SYNOP report. Downward-growing nimbostratus can have the vertical extent as most large upward-growing cumulus. This sometimes leads to the exclusion of nimbostratus from the group of vertical clouds by some independent meteorologists. Species and varieties, Nimbostratus is very thick, opaque, and featureless, precipitation-based supplementary features, Nimbostratus is a major precipitation cloud and produces the virga or praecipitatio features. The latter can achieve heavy intensity due to the vertical depth. Accessory cloud, Pannus frequently forms in precipitation and is coded CL7, genitus mother clouds, This genus type can form from cumulus and cumulonimbus. Mutatus mother clouds, Nimbostratus can form due to the transformation of altocumulus, altostratus and stratocumulus. Often, when an altostratus cloud thickens and descends into lower altitudes, lightning from an embedded cumulonimbus cloud may interact with the nimbostratus but only in the immediate area around it. The occurrence of cumulonimbus and nimbostratus together is uncommon, and usually only nimbostratus is found at a warm front, Nimbostratus pannus is an accessory cloud of nimbostratus that forms as a ragged layer in precipitation below the main cloud deck. Usually, nimbostratus is a sign of easily steady to powerful precipitation, however, precipitation does not occur at ground level in case of virga and accompanies other cloud types. Precipitation may last for days, depending on the speed of the warm or occluded front it accompanies. A nimbostratus virga cloud is the same as a normal nimbostratus cloud, stratus or stratocumulus usually forms when it clears. These were further divided into upper and lower types depending on altitude and it was then renamed nimbostratus, and published with the new name in the 1932 edition of the International Atlas of Clouds and of States of the Sky. This left cumulonimbus as the only nimbiform type as indicated by its root-name, national Science Digital Library - Nimbostratus Nimbostratus and Other Low Clouds
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Cumulus mediocris cloud
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Cumulus mediocris is a low to middle level cloud with some vertical extent of the genus cumulus, larger in vertical development than cumulus humilis. It also may exhibit small protuberances from the top and it may or may not show the cauliflower form characteristic of cumulus clouds. These clouds dont generally produce precipitation of more than light intensity, but may further advance into clouds such as cumulus congestus and Cumulonimbus. Species Cumulus mediocris achieves moderate vertical development, has medium-grey shading underneath and this larger species is also classified as a low cloud by some authorities and is coded CL2 on the synop report. Varieties, Cumulus mediocris is always opaque and therefore has no opacity-based varieties, a single pattern-based variety, radiatus, is sometime seen when the individual clouds are arranged into parallel rows. Precipitation-based supplementary features, Cumulus mediocris can produce virga and praecipitatio features, pileus, velum, arcus and tuba features are also occasionally seen with cumulus mediocris. Genitus mother clouds, Cumulus mediocris may form as a result of a transformation of altocumulus or stratocumulus. Mutatus mother clouds, This genus and species type may also be the result of a transformation of stratocumulus or stratus. These clouds are common in the advance of a front or in unstable atmospheric conditions such as an area of low pressure. They can grow into larger clouds which could bring rain, winds and in cases, thunder. If these clouds are present in the morning or early afternoon they show a significant instability in the atmosphere leading to storms later in the day. These clouds occur when there is more rising air than the Cumulus Humilis, like any cumulus cloud, this cloud requires convection before developing. This occurs when pockets of air around them become warmer and begin to rise, as the air rises, it condenses forming a cumulus humilis cloud as it continues to rise, a cumulus mediocris
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Arcus cloud
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An arcus cloud is a low, horizontal cloud formation, usually appearing as an accessory cloud to a cumulonimbus. Roll clouds and shelf clouds are the two types of arcus. Roll clouds also may arise in the absence of thunderstorms, forming along the cold air currents of some sea breeze boundaries. A shelf cloud is a low, horizontal, wedge-shaped arcus cloud, a shelf cloud is attached to the base of the parent cloud, which is usually a thunderstorm, but could form on any type of convective clouds. Rising cloud motion often can be seen in the part of the shelf cloud, while the underside often appears turbulent. Cool, sinking air from a storm clouds downdraft spreads out across the land surface and this outflow cuts under warm air being drawn into the storms updraft. As the lower cooler air lifts the warm moist air, its water condenses, creating a cloud which often rolls with the different winds above, people seeing a shelf cloud may believe they have seen a wall cloud. This is likely a mistake, since an approaching shelf cloud appears to form a wall made of cloud, a shelf cloud usually appears on the leading edge of a storm, and a wall cloud will usually be at the rear of the storm. A sharp, strong gust front will cause the lowest part of the edge of a shelf cloud to be ragged and lined with rising fractus clouds. In a severe case there will be vortices along the edge, a very low shelf cloud accompanied by these signs is the best indicator that a potentially violent wind squall is approaching. An extreme example of this phenomenon looks almost like a tornado and is known as a gustnado, a roll cloud is a low, horizontal, tube-shaped, and relatively rare type of arcus cloud. They differ from shelf clouds by being completely detached from other cloud features, roll clouds usually appear to be rolling about a horizontal axis. They are a wave called a soliton, which is a wave that has a single crest. One of the most famous frequent occurrences is the Morning Glory cloud in Queensland, Australia, one of the main causes of the Morning Glory cloud is the mesoscale circulation associated with sea breezes that develop over the Cape York Peninsula and the Gulf of Carpentaria. However, similar features can be created by downdrafts from thunderstorms and are not exclusively associated with coastal regions. Coastal roll clouds have been seen in places, including California, the English Channel, Shetland Islands, the North Sea coast, coastal regions of Australia. Archived from the original on July 15,2013
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Cumulonimbus cloud
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If observed during a storm, these clouds may be referred to as thunderheads. Cumulonimbus can form alone, in clusters, or along cold front squall lines and these clouds are capable of producing lightning and other dangerous severe weather, such as tornadoes. Cumulonimbus progress from overdeveloped cumulus congestus clouds and may develop as part of a supercell. Cumulonimbus is abbreviated Cb and are designated in the D2 family, towering cumulonimbus clouds are typically accompanied by smaller cumulus clouds. The cumulonimbus base may extend several miles across and occupy low to middle altitudes- formed at altitude from approximately 200 to 4,000 m, peaks typically reach to as much as 40,000 ft, with extreme instances as high as 70,000 ft or more. Well-developed cumulonimbus clouds are characterized by a flat, anvil-like top, the shelf of the anvil may precede the main clouds vertical component for many miles, and be accompanied by lightning. Occasionally, rising air parcels surpass the level and form an overshooting top culminating at the maximum parcel level. When vertically developed, this largest of all clouds usually extends through all three cloud regions, even the smallest cumulonimbus cloud dwarfs its neighbors in comparison. Cumulonimbus calvus, cloud with puffy top, similar to cumulus congestus which it develops from, cumulonimbus capillatus, cloud with cirrus-like, fibrous-edged top. Cumulonimbus incus, cloud with anvil top Arcus, low, horizontal cloud formation associated with the edge of thunderstorm outflow. Pannus, accompanied by a layer of fractus species cloud forming in precipitation. Pileus, small cap-like cloud over parent cumulonimbus, velum, a thin horizontal sheet that forms around the middle of a cumulonimbus. Incus, cumulonimbus with flat anvil-like cirriform top caused by wind shear where the air currents hit the inversion layer at the tropopause. Mamma or mammatus, consisting of bubble-like protrusions on the underside, tuba, column hanging from the cloud base which can develop into a funnel cloud or tornado. They are known to very low, sometimes just 20 feet above ground level. Flanking line is a line of small cumulonimbus or cumulus generally associated with severe thunderstorms, rain, precipitation that reaches the ground as liquid, often in a precipitation shaft. Virga, precipitation that evaporates before reaching the ground, cumulonimbus storm cells can produce torrential rain of a convective nature and flash flooding, as well as straight-line winds. Most storm cells die after about 20 minutes, when the precipitation causes more downdraft than updraft, causing the energy to dissipate
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Cumulus congestus cloud
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Cumulus congestus clouds, also known as towering cumulus, are a form of cumulus cloud that can be based in the low or middle height ranges. They achieve considerable vertical development in areas of deep, moist convection and they are an intermediate stage between cumulus mediocris and cumulonimbus. Cumulus congestus clouds are characteristic of areas of the atmosphere which are undergoing convection. They are often characterized by sharp outlines and great vertical development, because they are produced by strong updrafts, they are typically taller than they are wide, and cloud tops can reach 6 kilometres, or higher in the tropics. Cumulus congestus clouds are formed by the development of cumulus mediocris generally, the congestus species of cloud can only be found in the genus cumulus and is designated as towering cumulus by the International Civil Aviation Organization. Congestus clouds are capable of producing severe turbulence and showers of moderate to heavy intensity and this species is classified as vertical or multi-étage and is coded CL2 in the synop report. These clouds are too large and opaque to have any opacity or pattern-based varieties. Pyrocumulus is a convective cloud associated with volcanic eruptions and large-scale fires. Pyrocumulus is not recognized by the WMO as a genus or species. Cumulus congestus will mature into cumulonimbus calvus under conditions of sufficient instability and this transformation can be seen by the presence of smooth, fibrous, or striated aspects assumed by the clouds upper part. This cloud type produces precipitation, often in abundance and these clouds also produce fair weather waterspouts. This is often a sign that the front contains at least a few cumulonimbi amongst the nimbostratus rain clouds. The Cumulus Congestus cloud can form from the Cumulus mediocris cloud, the warm air that has fed the clouds formation from its birth is leading it to near freezing temperatures. As the air has been rising the temperatures have cooled, though it has not reached freezing yet therefore retaining its cauliflower like shape. This is the last stage before becoming a cumulonimbus cloud, turkey tower is slang for a narrow, individual towering cloud from a small cumulus cloud which develops and suddenly falls apart. Sudden development of towers could signify the breaking or weakening of a capping inversion. Altocumulus castellanus cloud Cumulus castellanus cloud Pileus American Meteorological Society - Glossary of Meteorology
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International Civil Aviation Organization
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The International Civil Aviation Organization, is a specialized agency of the United Nations. It codifies the principles and techniques of international air navigation and fosters the planning and development of air transport to ensure safe. Its headquarters are located in the Quartier International of Montreal, Quebec, ICAO defines the protocols for air accident investigation followed by transport safety authorities in countries signatory to the Convention on International Civil Aviation. The Air Navigation Commission is the body within ICAO. The Commission is composed of 19 Commissioners, nominated by the ICAOs contracting states, Commissioners serve as independent experts, who although nominated by their states, do not serve as state or political representatives. The development of Aviation Standards and Recommended Practices is done under the direction of the ANC through the process of ICAO Panels. Once approved by the Commission, standards are sent to the Council, the forerunner to ICAO was the International Commission for Air Navigation. It held its first convention in 1903 in Berlin, Germany, at the second convention in 1906, also held in Berlin,27 countries attended. The third convention, held in London in 1912 allocated the first radio callsigns for use by aircraft, ICAN continued to operate until 1945. Fifty-two countries signed the Convention on International Civil Aviation, also known as the Chicago Convention, in Chicago, Illinois, on 7 December 1944. Under its terms, a Provisional International Civil Aviation Organization was to be established, accordingly, PICAO began operating on 6 June 1945, replacing ICAN. The 26th country ratified the Convention on 5 March 1947 and, consequently PICAO was disestablished on 4 April 1947 and replaced by ICAO, in October 1947, ICAO became an agency of the United Nations linked to the United Nations Economic and Social Council. In April 2013 Qatar offered to serve as the new permanent seat of the Organization, according to the Globe and Mail, Qatars move was at least partly motivated by the pro-Israel foreign policy of Canadian Prime Minister Stephen Harper. Approximately one month later, Qatar withdrew its bid after a proposal to the ICAOs governing council to move the ICAO triennial conference to Doha was defeated by a vote of 22–14. The 9th edition of the Convention on International Civil Aviation includes modifications from 1948 up to year 2006, ICAO refers to its current edition of the Convention as the Statute, and designates it as ICAO Document 7300/9. The Convention has 19 Annexes that are listed by title in the article Convention on International Civil Aviation, as of March 2016, there are 191 ICAO members, consisting of 190 of the 193 UN members, plus the Cook Islands. Liechtenstein has delegated Switzerland to implement the treaty to make it applicable in the territory of Liechtenstein, Taiwan attended the 38th Session of the ICAO Assembly in 2013, but in 2016 was denied such an invitation, despite expressions of support from the United States for Taiwan to participate. However, the Republic of China under the name of Chinese Taipei is a member of International Air Transport Association, the Council of ICAO is elected by the Assembly every 3 years and consists of 36 members elected in 3 categories
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Mammatus cloud
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Mammatus, also known as mammatocumulus, is a meteorological term applied to a cellular pattern of pouches hanging underneath the base of a cloud. The name mammatus is derived from the Latin mamma, according to WMO International Cloud Atlas mamma is a cloud supplementary feature. Mammatus are most often associated with clouds and also severe thunderstorms. They often extend from the base of a cumulonimbus, but may also be found under altocumulus, altostratus, stratocumulus, in the United States, sky gazers may be most familiar with the very distinct and more common cumulonimbus mammatus. When occurring in cumulonimbus, mammatus are often indicative of a strong storm or maybe even a tornadic storm. Due to the intensely sheared environment in which form, aviators are strongly cautioned to avoid cumulonimbus with mammatus. They also attach to the bottom of other clouds, Mammatus may appear as smooth, ragged or lumpy lobes and may be opaque or translucent. The individual mammatus lobe average diameters of 1–3 km and lengths on average of 0.5 km, a lobe can last an average of 10 minutes, but a whole cluster of mamma can range from 15 minutes to a few hours. They are usually composed of ice, but also can be a mixture of ice, true to their ominous appearance, mammatus clouds are often harbingers of a coming storm or other extreme weather system. Typically composed primarily of ice, they can extend for hundreds of miles in each direction, while they may appear foreboding they are merely the messengers - appearing around, before or even after severe weather. The following are the mechanisms, each described with its shortcomings. However, the air will warm more slowly than the sub-cloud. Because of the warming, the cloud/sub-cloud layer destabilizes and convective overturning can occur. Cooling due to hydrometeor fallout is a second proposed formation mechanism, as hydrometeors fall into the dry sub-cloud air, the air containing the precipitation cools due to evaporation or sublimation. One problem with this theory is that show that cloud-base evaporation does not always produce mammatus. This mechanism could be responsible for the earliest stage of development, there may also be destabilization at cloud base due to melting. If the cloud base exists near the line, then the cooling in the immediate air caused by melting can lead to convective overturning. However, this strict temperature environment is not always present, the above processes specifically relied on the destabilization of the sub-cloud layer due to adiabatic or latent heating effects
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Funnel cloud
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A funnel cloud is a funnel-shaped cloud of condensed water droplets, associated with a rotating column of wind and extending from the base of a cloud but not reaching the ground or a water surface. A funnel cloud is visible as a cone-shaped or needle like protuberance from the main cloud base. Funnel clouds form most frequently in association with supercell thunderstorms, if a funnel cloud touches the ground it becomes a tornado. Most tornadoes begin as funnel clouds, but many funnel clouds do not make ground contact, also, a tornado does not necessarily need to have an associated condensation funnel—if strong cyclonic winds are occurring at the surface, then the feature is a tornado. Some tornadoes may appear only as a debris swirl, with no obvious funnel cloud extending below the cloud base. In cloud nomenclature, any funnel- or inverted-funnel-shaped cloud depending from cumulus or cumulonimbus clouds is technically described as a feature called tuba. The terms tuba and funnel cloud are nearly but not exactly synonymous, cold-air funnel clouds are usually short-lived and generally much weaker than the vortices produced by supercells. Although cold-air funnels rarely make contact, they may touch down briefly. They are a common sight along the Pacific Coast of the United States, on July 29,2013, a cold-core funnel cloud touched down as an EF0 tornado in Ottawa, Canada, causing extensive damage in the form of downed trees on a golf course. No advance weather watches or warnings were issued by Environment Canada, Tornado Dust devil Landspout USA Today article on small vortices TORRO Tornado FAQ Cold-core waterspouts over Lake Michigan in fall 2006 Bluestein, Howard B. A Funnel Cloud in a Convective Cloud Line to the Rear of a Surface Cold Front
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Wall cloud
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A wall cloud is a large, localized, persistent, and often abrupt lowering of cloud that develops beneath the surrounding base of a cumulonimbus cloud and from which tornadoes sometimes form. It is typically beneath the base portion of a thunderstorm. Rotating wall clouds are an indication of a mesocyclone in a thunderstorm, many wall clouds do rotate, however some do not. Wall clouds are formed by a known as entrainment, when an inflow of warm, moist air rises and converges, overpowering wet. As the warm air continues to entrain the cooler air, the air temperature drops, as this air continues to rise, it becomes more saturated with moisture, which results in additional cloud condensation, sometimes in the form of a wall cloud. Wall clouds may form as a descending of the base or may form as rising scud comes together. Wall clouds can be anywhere from a fraction of 1.6 km wide to over 8 km across, Wall clouds form in the inflow region, on the side of the storm coinciding with the direction of the steering winds. In the Northern Hemisphere wall clouds typically form at the south or southwest end of a supercell, rotating wall clouds are visual evidence of a mesocyclone. Some wall clouds have a similar to an eye, as in a mesoscale convective vortex. Attached to many wall clouds, especially in moist environments, is a cauda and it can be thought of as an extension of the wall cloud in that not only is the tail cloud connected to the wall cloud but also that condensation forms for a similar reason. Cloud elements may be seen to be moving into the wall cloud, most movement is horizontal, but some rising motion is often apparent as well. Some wall clouds also have a band of cloud fragments encircling the top of the cloud where it meets the ambient cloud base. Another accessory cloud is the flumen, commonly known as the beavers tail and it is formed by the warm, humid inflow of a strong thunderstorm, and is often mistaken for tornadoes. Although the presence of a flumen is associated with tornado risk, many storms contain shelf clouds, which are often mistaken for wall clouds, since an approaching shelf cloud appears to form a wall made of cloud and may contain turbulent motions. Wall clouds are inflow clouds and tend to slope inward, or toward the area of a storm. Shelf clouds, on the hand, are outflow clouds that jut outward from the storm. Also, shelf clouds tend to move away from the precipitation area of a storm. Shelf clouds most often appear on the edge of a thunderstorm as they are formed by condensation from cool outflow of the storm that lifts warmer air in the ambient environment
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Overshooting top
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An overshooting top is a dome-like protrusion that shoots out of the top of the anvil of a thunderstorm. When an overshooting top is present for 10 minutes or longer and this point of equilibrium is often marked by the tropopause. Rather than continuing to rise into the stratosphere, the vertical cloud growth abruptly stops, an overshooting top forms when a thunderstorms updraft, due to momentum from rapid ascent and strength of lifting, protrudes its equilibrium level, forming a dome-like structure on top of the anvil. This can occur with any cumulonimbus cloud when instability is high, whereas anvils form at the equilibrium level, overshooting tops continue to the maximum parcel level. Most thunderstorms will have a top at some point in their life cycle. In weaker thunderstorms, the top is short-lived, and often takes on a wispy appearance. If the overshooting top is rising and falling in a fashion, then it could indicate the storm is pulsing. An overshooting top lasting for more than 10 minutes is a sign of a strong updraft in a thunderstorm, if the overshooting top is continuous it means the storm is probably a strong supercell. During a strong tornado, the overshooting top might roll over or fold over as new activity climbs up the back while the front of the overshooting top collapses into the storm. During a long-track tornado, the top of the storm, including the overshooting top. A storm powerful enough to produce an overshooting top will have the following, Heavy rain. Strong wind, the clouds have powerful winds churning inside them. These winds are likely to be felt at the surface as well, hail, if the updraft is strong enough to produce an overshooting top it can also carry large hail. Lightning, this is sure to be a thunderstorm
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Hot tower
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A hot tower is a tropical cumulonimbus cloud that penetrates the tropopause, i. e. it reaches out of the lowest layer of the atmosphere, the troposphere, into the stratosphere. In the tropics, the tropopause typically lies at least 15 kilometres above sea level and these towers are called hot because they rise high due to the large amount of latent heat released as water vapor condenses into liquid and freezes into ice. The presence of hot towers with a tropical cyclones eyewall can indicate strengthening is more likely during the six hours. The hot tower hypothesis was proposed in 1958 by Herbert Riehl, prior to 1958, the mechanism driving the global-scale circulation pattern called Hadley cells was poorly understood. The large horizontal extent of convective cells provides a buffer from the dry air surrounding the convective region that allows the parcel to rise at nearly the moist adiabatic lapse rate. NOAA also defined the term Towering cumulonimbus in 2009, in 2007, the National Aeronautics and Space Administration hypothesized that the wind shear between the eye and the eyewall could enhance updraft and be a purely dynamic generator of convection. Hot towers may appear when the hurricane is about to intensify, a particularly tall hot tower rose above Hurricane Bonnie in August 1998 as the storm intensified before striking North Carolina, United States. Bonnie caused more than $1 billion in damage and three deaths, according to the National Oceanic and Atmospheric Administration and the National Hurricane Center, Hot towers are also known to form when a tropical cyclone is about to undergo an explosive intensification. List of cloud types Tropical cyclone Riehl, Herbert, Malkus, on the heat balance in the equatorial trough zone. Some Views On Hot Towers after 50 Years of Tropical Field Programs, UCAR slides, Hot Towers and Hurricanes, Early Observations, Theories and Models
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Fog
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Fog consists of visible cloud water droplets or ice crystals suspended in the air at or near the Earths surface. Fog can be considered a type of low-lying cloud and is influenced by nearby bodies of water, topography. In turn, fog has affected many human activities, such as shipping, travel, the term fog is typically distinguished from the more generic term cloud in that fog is low-lying, and the moisture in the fog is often generated locally. By definition, fog reduces visibility to less than 1 kilometre, for aviation purposes in the UK, a visibility of less than 5 kilometres but greater than 999 metres is considered to be mist if the relative humidity is 70% or greater, below 70%, haze is reported. Fog forms when the difference between air temperature and dew point is less than 2.5 °C or 4 °F, Fog begins to form when water vapor condenses into tiny liquid water droplets suspended in the air. Water vapor normally begins to condense on condensation nuclei such as dust, ice, Fog, like its elevated cousin stratus, is a stable cloud deck which tends to form when a cool, stable air mass is trapped underneath a warm air mass. Fog normally occurs at a relative humidity near 100% and this occurs from either added moisture in the air, or falling ambient air temperature. However, fog can form at lower humidities, and can fail to form with relative humidity at 100%. At 100% relative humidity, the air cannot hold additional moisture, thus, Fog can form suddenly and can dissipate just as rapidly. The sudden formation of fog is known as flash fog, Fog commonly produces precipitation in the form of drizzle or very light snow. Drizzle occurs when the humidity of fog attains 100% and the cloud droplets begin to coalesce into larger droplets. This can occur when the fog layer is lifted and cooled sufficiently, drizzle becomes freezing drizzle when the temperature at the surface drops below the freezing point. The inversion boundary varies its altitude primarily in response to the weight of the air above it, the marine layer, and any fogbank it may contain, will be squashed when the pressure is high, and conversely, may expand upwards when the pressure above it is lowering. Fog can form in a number of ways, depending on how the cooling that caused the condensation occurred, radiation fog is formed by the cooling of land after sunset by thermal radiation in calm conditions with clear sky. The warm ground produces condensation in the air by heat conduction. In perfect calm the fog layer can be less than a meter deep, radiation fogs occur at night, and usually do not last long after sunrise, but they can persist all day in the winter months especially in areas bounded by high ground. Radiation fog is most common in autumn and early winter, examples of this phenomenon include the Tule fog. Ground fog is fog that obscures less than 60% of the sky, advection fog occurs when moist air passes over a cool surface by advection and is cooled
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Accessory cloud
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An accessory cloud is a cloud which is dependent on a larger cloud system for its development and continuance. It is often an appendage but also can be adjacent to the parent cloud system, the condensation funnel of funnel clouds and tornadoes are also accessory clouds. They are associated with deep moist convection and especially cumulonimbus, the primary cloud producing thunderstorms, the pileus and mammatus types can form at various altitude ranges depending on the main clouds with which they are associated. The World Meteorological Organization classifies most accessory clouds as supplementary features, the height range classification of a supplementary feature is the same as the parent cloud. As an example, the cloud forms at high altitude but is not classisfied by the WMO as a high cloud because of its association with the genus cumulonimbus. It is very rare for any accessory cloud to generate its own precipitation, however, the parent cloud may generate precipitation. Precipitation from the parent cloud is often confused with the accessory cloud and observers think that the precipitation is actually falling from the accessory cloud
