High clouds streaking upward of 45,000 feet above the ground are called Cirrus, Cirrocumulus or Cirrostratus, while lower-lying Cumulus or Cumulonimbus clouds are usually spotted anywhere from the Earth's surface to 6,500 feet above land.
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Even in "Certain Women" in 2016, when Kelly Reichardt wanted a performance so minimal and restrained that she told Dern not to move her foot while lying in bed, Dern found a way to express the contradictory desires, impulses and disappointments that were driving her character's choices by setting her mouth and squinting so that her eyes appeared to be covered with a vague cirrostratus scrim.
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Cirrostratus fibratus is a type of cirrostratus cloud. The name cirrostratus fibratus is derived from Latin, meaning "fibrous". Cirrostratus fibratus is one of the two most common forms that cirrostratus often takes, with the other being cirrostratus nebulosus. They are formed from strong, continuous winds blowing at high altitudes, and they often cover a large portion of the sky.
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Cirrostratus nebulosus is a species of high-level cirrostratus cloud. The name cirrostratus nebulosus is derived from Latin, the adjective nebulosus meaning "full of vapor, foggy, cloudy, dark". Cirrostratus nebulosus is one of the two most common forms that cirrostratus often takes, with the other being cirrostratus fibratus. The nebulosus species is featureless and uniform, while the fibratus species has a fibrous appearance.
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A cirrostratus cloud Cirrostratus clouds can appear as a milky sheen in the sky or as a striated sheet. They are sometimes similar to altostratus and are distinguishable from the latter because the sun or moon is always clearly visible through transparent cirrostratus, in contrast to altostratus which tends to be opaque or translucent. Cirrostratus come in two species, fibratus and nebulosus. The ice crystals in these clouds vary depending upon the height in the cloud.
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A cirrostratus cloud Cirrostratus clouds, a very high ice-crystal form of stratiform clouds, can appear as a milky sheen in the sky or as a striated sheet. They are sometimes similar to altostratus and are distinguishable from the latter because the sun or moon is always clearly visible through transparent cirrostratus, in contrast to altostratus which tends to be opaque or translucent. Cirrostratus come in two species, fibratus and nebulosus. The ice crystals in these clouds vary depending upon the height in the cloud.
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Of the non-convective stratiform group, high-level cirrostratus comprises two species. Cirrostratus nebulosus has a rather diffuse appearance lacking in structural detail. Cirrostratus fibratus is a species made of semi-merged filaments that are transitional to or from cirrus. Mid-level altostratus and multi-level nimbostratus always have a flat or diffuse appearance and are therefore not subdivided into species.
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A solar halo There are three main genera in the family of high clouds: cirrus, cirrocumulus, and cirrostratus. Cirrostratus clouds commonly produce halos because they are composed almost entirely of ice crystals. Cirrocumulus and cirrostratus are sometimes informally referred to as "cirriform clouds" because of their frequent association with cirrus. They are given the prefix "cirro-", but this refers more to their altitude range than their physical structure.
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Cirri and cirrostratus clouds have been very prevalent during the day, and cumulostratus during the night.
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Cirrocumulus in its pure form is actually a high cumuliform genus, and cirrostratus is stratiform, like altostratus and lower based sheet clouds.
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When a warm front approaches, cirrostratus clouds become thicker and descend forming altostratus clouds, and rain usually begins 12 to 24 hours later.
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When a warm front approaches, cirrostratus clouds become thicker and descend forming altostratus clouds, and rain usually begins 12 to 24 hours later.
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Cirrostratus nebulosus (V-22) merging into darker altostratus translucidus (V-47) Abbreviation: Cs Clouds of the genus cirrostratus consist of mostly continuous, wide sheets of cloud that covers a large area of the sky. It is formed when convectively stable moist air cools to saturation at high altitude, forming ice crystals.Burroughs, William James; Crowder, Bob (January 2007). Weather, p.215.
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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 . Like lower-altitude cumuliform and stratocumuliform clouds, cirrocumulus signifies convection. Unlike other high-altitude tropospheric clouds like cirrus and cirrostratus, cirrocumulus includes a small amount of liquid water droplets, although these are in a supercooled state.
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Cirrostratus fibratus may often develop from either cirrus fibratus or cirrus spissatus cloud. Precipitation is often imminent behind these clouds; however, they are not a precipitation-producing cloud.
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Fog City Press, San Francisco. . Frontal cirrostratus is a precursor to rain or snow if it thickens into mid-level altostratus and eventually nimbostratus as the weather front moves closer to the observer.
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Condensation trails with Cirrocumulus homogenitus (Cca) and Cirrostratus homogenitu (Csa) observed over Barcelona (Spain, November 2010). Despite the fact that the three genera of high clouds, Cirrus, Cirrocumulus and Cirrostratus, form at the top of the troposphere, far from the earth surface, they may have an anthropogenic origin. In this case, the process that causes their formation is almost always the same: commercial and military aircraft flight. Exhaust products from the combustion of the kerosene expelled by engines provide water vapor to this region of the troposphere.
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Although altostratus forms mostly in the middle level of the troposphere, strong frontal lift can push it into the lower part of the high- level. The main high-level stratiform cloud is cirrostratus which is composed of ice crystals that often produce halo effects around the sun. Cirrostratus forms at altitudes of in high latitudes, in temperate latitudes, and in low, tropical latitudes. Of the non-stratiform clouds, cumulonimbus and cumulus congestus are the most closely related to nimbostratus because of their vertical extent and ability to produce moderate to heavy precipitation.
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A circumhorizontal arc over Idaho, June 2006 Cirrus clouds, like cirrostratus clouds, can produce several optical effects, such as halos around the sun and moon. Halos are caused by interaction of the light with hexagonal ice crystals present in the clouds, which, depending on their shape and orientation, can result in a wide variety of white and colored rings, arcs and spots in the sky. Common halo varieties are the 22° halo, sun dogs, the circumzenithal arc and the circumhorizontal arc (also known as fire rainbows). Halos produced by cirrus clouds tend to be more pronounced and colorful than those caused by cirrostratus.
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Mid-level clouds form from to in polar areas, in temperate areas, and in tropical areas. The high-level cloud, cirrocumulus, is a stratocumuliform cloud of limited convection. The other clouds in this level are cirrus and cirrostratus. High clouds form in high latitudes, in temperate latitudes, and in low, tropical latitudes.
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Ice crystals are the predominant component, and typically, the ice crystals cause the supercooled water drops in the cloud to rapidly freeze, transforming the cirrocumulus into cirrostratus. This process can also produce precipitation in the form of a virga consisting of ice or snow. Thus, cirrocumulus clouds are usually short-lived., p.
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If a cirrus homogenitus cloud changes fully to any of the high-level genera, they are termed cirrus, cirrostratus, or cirrocumulus homomutatus. Stratus cataractagenitus (Latin for 'cataract-made') are generated by the spray from waterfalls. Silvagenitus (Latin for 'forest-made') is a stratus cloud that forms as water vapor is added to the air above a forest canopy.
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Re-entering the warmer waters of the Western Pacific Ocean, Nida's winds restrengthened to 150 mph (250 km/h). During the night of May 18, the typhoon began to weaken. Infrared satellite imagery showed the eye being obscured by high cirrostratus clouds, indicative of the weakening typhoon. The eyewall became significantly disorganized as Nida continued to recurve to the northeast.
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Noctilucent cloud over Estonia Noctilucent clouds are thin clouds that come in a variety of forms based from about and occasionally seen in deep twilight after sunset and before sunrise. ;Type 1 : Veils, very tenuous stratiform; resembles cirrostratus or poorly defined cirrus. ;Type 2 : Long stratocumuliform bands, often in parallel groups or interwoven at small angles. More widely spaced than cirrocumulus bands.
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The heights of various cloud genera including high, middle, low, and vertical Cirrus clouds are one of three different genera of high-étage (high-level) clouds. High-étage clouds form at and above in temperate regions. The other two genera, cirrocumulus and cirrostratus, are also high clouds. In the intermediate range, from in temperate regions, are the mid-étage clouds.
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Noctilucent clouds have four major types based on physical structure and appearance. Type I veils are very tenuous and lack well-defined structure, somewhat like cirrostratus or poorly defined cirrus. Type II bands are long streaks that often occur in groups arranged roughly parallel to each other. They are usually more widely spaced than the bands or elements seen with cirrocumulus clouds.
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The long- term behaviour of polar mesospheric cloud frequency has been found to vary inversely with solar activity. PMC's have four major types based on physical structure and appearance. Type I veils are very tenuous and lack well-defined structure, somewhat like cirrostratus or poorly defined cirrus. Type II bands are long streaks that often occur in groups arranged roughly parallel to each other.
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A vast shield of cirrus clouds accompanying the west side of Hurricane Isabel Cirrus forms from tropical cyclones, and is commonly seen fanning out from the eyewalls of hurricanes. A large shield of cirrus and cirrostratus typically accompanies the high altitude outflow of hurricanes or typhoons, and these can make the underlying rain bands—and sometimes even the eye—difficult to detect in satellite photographs.
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As a result of more recent research, the World Meteorological Organization now recognizes four major forms that can be subdivided. Type I veils are very tenuous and lack well- defined structure, somewhat like cirrostratus or poorly defined cirrus. Type II bands are long streaks that often occur in groups arranged roughly parallel to each other. They are usually more widely spaced than the bands or elements seen with cirrocumulus clouds.
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In the later case, depending on the wind conditions Cca may evolve to Cirrus homogenitus (aCi), or Cirrostratus homogenitus (Csa). The existence and persistence of these three types of high anthropogenic clouds may indicate the approximation of air stability. In some cases, when there is a large density of air traffic, these high homogenitus may inhibit the formation of natural high clouds, because the contrails capture most of the water vapor.
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Diamond dust is often associated with halos, such as sun dogs, light pillars, etc. Like the ice crystals in cirrus or cirrostratus clouds, diamond dust crystals form directly as simple hexagonal ice crystals — as opposed to freezing drops — and generally form slowly. This combination results in crystals with well defined shapes - usually either hexagonal plates or columns - which, like a prism, can reflect and/or refract light in specific directions.
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Cirrostratus nebulosus are formed by gently rising air. The cloud is often hard to see unless the sun shines through it at the correct angle, forming a halo. While usually very light, the cloud may also be very dense, and the exact appearance of the cloud can vary from one formation to another. In the winter, precipitation often follows behind these clouds; however, they are not a precipitation-producing cloud.
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Atmospheric optical phenomena like halos were used as part of weather lore, which was an empirical means of weather forecasting before meteorology was developed. They often do indicate that rain will fall within the next 24 hours, since the cirrostratus clouds that cause them can signify an approaching frontal system. Other common types of optical phenomena involving water droplets rather than ice crystals include the glory and rainbow.
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The high étage ranges from altitudes of in the polar regions, in the temperate regions and in the tropical region. The major high-level cloud types comprise cirrus, cirrocumulus, and cirrostratus. The middle étage extends from above surface at any latitude as high as near the poles, at mid latitudes, and in the tropics. Altocumulus and Altostratus are the main cloud types found in the middle levels of the troposphere.
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If the cloud is a cirrus castellanus, there might be instability at the high altitude level. When the clouds deepen and spread, especially when they are of the cirrus radiatus variety or cirrus fibratus species, this usually indicates an approaching weather front. If it is a warm front, the cirrus clouds spread out into cirrostratus, which then thicken and lower into altocumulus and altostratus. The next set of clouds are the rain- bearing nimbostratus clouds.
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Morning cumulus humilis clouds are signs of an unstable atmosphere. Larger clouds or 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 precede a storm. Cumulus humilis are sometimes seen beneath cirrostratus clouds, which block some of the heat from the sun and thus create an inversion, causing any cumuliform clouds to flatten and become cumulus humilis.
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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 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 undulatus Altostratus is formed by the lifting of a large mostly stable air mass that causes invisible water vapor to condense into cloud.
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Nocturnal light pillars caused by light reflected through ice fog in Cambridge Bay, Nunavut, Canada A light pillar is an atmospheric optical phenomenon in which a vertical beam of light appears to extend above and/or below a light source. The effect is created by the reflection of light from tiny ice crystals that are suspended in the atmosphere or that comprise high-altitude clouds (e.g. cirrostratus or cirrus clouds).Colonne lumineuse by the World Meteorological Organization.
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There are many types of ice halos. They are produced by the ice crystals in cirrus or cirrostratus clouds high in the upper troposphere, at an altitude of to , or, during very cold weather, by ice crystals called diamond dust drifting in the air at low levels. The particular shape and orientation of the crystals are responsible for the types of halo observed. Light is reflected and refracted by the ice crystals and may split into colors because of dispersion.
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Marestail shows moisture at high altitude, signalling the later arrival of wet weather. Along with pressure tendency, the condition of the sky is one of the more important parameters used to forecast weather in mountainous areas. Thickening of cloud cover or the invasion of a higher cloud deck is indicative of rain in the near future. High thin cirrostratus clouds can create halos around the sun or moon, which indicates an approach of a warm front and its associated rain.
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Supercooled nitric acid and water PSC's, sometimes known as type 1, typically have a stratiform appearance resembling cirrostratus or haze, but because they are not frozen into crystals, do not show the pastel colours of the nacreous types. This type of PSC has been identified as a cause of ozone depletion in the stratosphere. The frozen nacreous types are typically very thin with mother-of-pearl colorations and an undulating cirriform or lenticular (stratocumuliform) appearance. These are sometimes known as type 2.
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Cirrocumulus usually only forms in patches. If it forms in patches with cirrus or cirrostratus and the clouds spread across the sky, it usually means rain in 8–10 hours (can be more if the front is slow-moving). Only small patches of cirrocumulus and perhaps some wisps of cirrus usually mean a continuation of good weather (although this may also be seen in conjunction with showers and thunderstorms). If it is seen after rain, it usually means improving the weather.
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In his late twenties, Luke Howard wrote the Essay on the Modification of Clouds, which was published in 1803. Howard's system was similar to the recently popularized Linnaean classification system developed by taxonomist Carl von Linne. Howard named the three principal categories of clouds – cumulus, stratus, and cirrus, as well as a series of intermediate and compound modifications, such as cirrostratus and cirrocumulus, in order to accommodate the transitions occurring between the forms. Howard's classification system applied the recently popularized Linnean principles of natural history classification.
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The Moon's appearance, like the Sun's, can be affected by Earth's atmosphere. Common optical effects are the 22° halo ring, formed when the Moon's light is refracted through the ice crystals of high cirrostratus clouds, and smaller coronal rings when the Moon is seen through thin clouds. The illuminated area of the visible sphere (degree of illumination) is given by (1-\cos e)/2=\sin^2(e/2), where e is the elongation (i.e., the angle between Moon, the observer (on Earth) and the Sun).
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Nonconvective stratiform clouds appear in stable airmass conditions and, in general, have flat, sheet-like structures that can form at any altitude in the troposphere. The stratiform group is divided by altitude range into the genera cirrostratus (high-level), altostratus (mid-level), stratus (low-level), and nimbostratus (multi-level). Fog is commonly considered a surface-based cloud layer. The fog may form at surface level in clear air or it may be the result of a very low stratus cloud subsiding to ground or sea level.
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White cumulus clouds appeared over Dhaka, Bangladesh, when significant flooding was underway in many parts of the country. Along with pressure tendency, the condition of the sky is one of the more important parameters used to forecast weather in mountainous areas. Thickening of cloud cover or the invasion of a higher cloud deck is indicative of rain in the near future. At night, high thin cirrostratus clouds can lead to halos around the Moon, which indicate the approach of a warm front and its associated rain.
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Right-hand sun dog in Salem, Massachusetts, Oct 27, 2012. Also visible are a Parry arc, an upper tangent arc, a 22° halo and part of the parhelic circle. Sun dogs are commonly caused by the refraction and scattering of light from plate-shaped hexagonal ice crystals either suspended in high and cold cirrus or cirrostratus clouds, or drifting in freezing moist air at low levels as diamond dust. The crystals act as prisms, bending the light rays passing through them with a minimum deflection of 22°.
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Most often, stratocumulus produce no precipitation, and when they do, it is generally only light rain or snow. 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. They are also often seen underneath the cirrostratus and altostratus sheets that often precede a warm front, as these higher clouds decrease the sun's heat and therefore convection, causing any cumulus clouds to spread out into stratocumulus clouds.
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The bar of a mature tropical cyclone is a very dark gray-black layer of cloud appearing near the horizon as seen from an observer preceding the approach of the storm, and is composed of dense stratocumulus clouds. Cumulus and cumulonimbus clouds bearing precipitation follow immediately after the passage of the wall-like bar. Altostratus, cirrostratus and cirrus clouds are usually visible in ascending order above the top of the bar, while the wind direction for an observer facing toward the bar is typically from the left and slightly behind the observer.
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The ice crystals responsible for halos are typically suspended in cirrus or cirrostratus clouds in the upper troposphere (), but in cold weather they can also float near the ground, in which case they are referred to as diamond dust. The particular shape and orientation of the crystals are responsible for the type of halo observed. Light is reflected and refracted by the ice crystals and may split into colors because of dispersion. The crystals behave like prisms and mirrors, refracting and reflecting light between their faces, sending shafts of light in particular directions.
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Nimbostratus occurs along a warm front or occluded front where the slowly rising warm air mass creates nimbostratus along with shallower stratus clouds producing less rain, these clouds being preceded by higher- level clouds such as cirrostratus and altostratus. Often, when an altostratus cloud thickens and descends into lower altitudes, it will become nimbostratus. Nimbostratus, unlike cumulonimbus, is not associated with thunderstorms, however at an unusually unstable warm front caused as a result of the advancing warm air being hot, humid and unstable, cumulonimbus clouds may be embedded within the usual nimbostratus. Lightning from an embedded cumulonimbus cloud may interact with the nimbostratus but only in the immediate area around it.
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A halo around the Moon and a pair of moon dogs over the observatory at the University of Alberta in Edmonton, Canada. A moon dog, moondog, or mock moon, (scientific name paraselene, plural paraselenae, meaning "beside the moon") is a relatively rare bright circular spot on a lunar halo caused by the refraction of moonlight by hexagonal-plate-shaped ice crystals in cirrus or cirrostratus clouds. A pair of moon dogs over Didcot, England Moon dogs appear as part of the 22° halo, roughly 10 Moon diameters outside the Moon. They are exactly analogous to sun dogs, but are rarer because the Moon must be bright, about quarter moon or more, for the moon dogs to be observed.
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The main ways water vapor is added to the air are: wind convergence into areas of upward motion, precipitation or virga falling from above, daytime heating evaporating water from the surface of oceans, water bodies or wet land, transpiration from plants, cool or dry air moving over warmer water, and lifting air over mountains. Water vapor normally begins to condense on condensation nuclei such as dust, ice, and salt in order to form clouds. Elevated portions of weather fronts (which are three-dimensional in nature) force broad areas of upward motion within the Earth's atmosphere which form clouds decks such as altostratus or cirrostratus. Stratus is a stable cloud deck which tends to form when a cool, stable air mass is trapped underneath a warm air mass.
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Circumzenithal arc in Salem, Massachusetts, Oct 27, 2012. Also visible are a supralateral arc, Parry arc (upper suncave), and upper tangent arc. The circumzenithal arc, also called the circumzenith arc (CZA), upside-down rainbow, and the Bravais arc,"Mémoire sur les halos et les phénomènes optiques qui les accompagnent", J. de l' École Royale Polytechnique 31(18), 1-270, A. Bravais, 1847 is an optical phenomenon similar in appearance to a rainbow, but belonging to the family of halos arising from refraction of sunlight through ice crystals, generally in cirrus or cirrostratus clouds, rather than from raindrops. The arc is located at a considerable distance (approximately 46°) above the observed Sun and at most forms a quarter of a circle centered on the zenith.
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Interaction of visible light with the ice crystals in them produces, below, optical phenomena such as sun dogs and halos. Cirrus is known to raise the temperature (due the heat released as water vapor freezes) of the air beneath the main cloud layer, by an average of 10 °C (18 °F), When the individual filaments become so extensive as to be virtually indistinguishable, one from another, they form a sheet of high cloud called cirrostratus. Convection at high altitudes can produce another high-based genus of cloud, cirrocumulus, with a pattern of small cloud tufts containing droplets of supercooled water. Some polar stratospheric clouds can resemble cirrus, and noctilucent clouds typically become structured in ways similar to those of cirrus.
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The first clouds that indicate an approaching warm front tend to be mostly high cirrus at first, changing to cirrostratus as the front approaches. However, if cirrocumulus also appears, there is greater airmass instability approaching ahead of the front. When these high clouds progressively invade the sky and the barometric pressure begins to fall, precipitation associated with the disturbance is likely about 6 to 8 hours away. A thickening and lowering of these high clouds into middle-stage altostratus or altocumulus is a good sign the warm front or low has moved closer and precipitation may begin within less than six hours. Once the clouds have thickened to from the earth’s surface, precipitation can begin to fall from heavy nimbostratus.
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