Cirrus is a genus of high cloud made of ice crystals. Cirrus clouds typically appear delicate and wispy with white strands. Cirrus are usually formed when warm, dry air rises, causing water vapor deposition onto rocky or metallic dust particles at high altitudes. Globally, they form anywhere between 4,000 and 20,000 meters above sea level, with the higher elevations usually in the tropics and the lower elevations in more polar regions.
In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may compose the droplets and crystals. On Earth, clouds are formed as a result of saturation of the air when it is cooled to its dew point, or when it gains sufficient moisture from an adjacent source to raise the dew point to the ambient temperature.
Altocumulus is a middle-altitude cloud genus that belongs mainly to the stratocumuliform physical category characterized by globular masses or rolls in layers or patches, the individual elements being larger and darker than those of cirrocumulus and smaller than those of stratocumulus. 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. A sheet of partially conjoined altocumulus perlucidus is sometimes found preceding a weakening warm front, where the altostratus is starting to fragment, resulting in patches of altocumulus perlucidus between the areas of altostratus. Altocumulus is also commonly found between the warm and cold fronts in a depression, although this is often hidden by lower clouds.
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 to 12 km. 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. 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. 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.
Cumulus castellanus is an unofficial name of a species of cumulus cloud that is distinctive because it displays multiple towers arising from its top, indicating significant vertical air movement. It is a misnomer for cumulus congestus and correspondingly can be an indicator of forthcoming showers and thunderstorms. The World Meteorological Organization and the American Meteorological Society do not recognize cumulus castellanus as a distinct species, but instead classify all towering cumulus clouds as Cumulus congestus.
Cirrus intortus is a variety of cirrus cloud. The name cirrus intortus is derived from Latin, meaning "twisted, wound". The variety of intortus clouds is specific to cirrus clouds, and they appear as interwound strands of cirrus clouds with a purely random pattern. The filaments are often curved in a very irregular pattern.
Cirrus fibratus or also called Cirrus filosus is a species of cirrus cloud. The name cirrus fibratus is derived from Latin, meaning "fibrous". These clouds are similar to cirrus uncinus, commonly known as "mares' tails"; however, fibratus clouds do not have tufts or hooks at the end. The filaments are usually separate from one another.
Cirrus floccus is a type of cirrus cloud. The name cirrus floccus is derived from Latin, meaning "a lock of wool". Cirrus floccus occurs as small tufts of cloud, usually with a ragged base. The cloud can have virga falling from it, but the precipitation does not reach the ground. The individual tufts are usually isolated from each other. At formation, the cirrus floccus clouds are bright white and can be mistaken for altocumulus clouds; however, after a few minutes, the brightness begins to fade, indicating they are made up of pure ice, and are therefore at a higher level.
Cirrus duplicatus is a variety of cirrus cloud. The name cirrus duplicatus is derived from Latin, meaning "double". The duplicatus variety of cirrus clouds occurs when there are at least two layers of cirrus clouds. Most of the time, occurrences of cirrus fibratus and cirrus uncinus are in the duplicatus form. Like stratus clouds, cirrus clouds are often seen in the duplicatus form.
Cirrus radiatus is a variety of cirrus cloud. The name cirrus radiatus is derived from Latin, meaning "rayed, striped". This variety of cirrus clouds occurs in parallel bands that often cover the entire sky and appear to converge at a single point or two opposite points on the horizon. Cirrus radiatus is often partly made up of cirrocumulus or cirrostratus.
Cirrus vertebratus is a type of cirrus cloud. The name cirrus vertebratus is derived from Latin, meaning "jointed, articulated, vertebrated". Like cirrus intortus, the vertebratus species is exclusive to the cirrus genus. Cirrus vertebratus gives the impression of vertebrae in a spinal column, ribs, or a fish skeleton.
Cirrocumulus castellanus or Cirrocumulus castellatus is a type of cirrocumulus cloud. Castellanus is from the Latin meaning "of a castle". These clouds appear as round turrets that are rising from either a lowered line or sheet of clouds. Cirrocumulus castellanus is an indicator of atmospheric instability at the level of the cloud. The clouds form when condensation occurs in the base cloud, causing latent heating to occur. This causes air to rise from the base cloud, and if the air ascends into conditionally unstable air, cirrocumulus castellanus will form.
Cirrocumulus floccus is a type of cirrocumulus cloud. The name cirrocumulus floccus is derived from Latin, meaning "a lock of wool". Cirrocumulus floccus appears as small tufts of cloud with rounded heads, but ragged bottoms. The cloud can produce virga, precipitation that evaporates before reaching the ground. Like cirrocumulus castellanus, cirrocumulus floccus is an indicator of atmospheric instability at the level of the cloud. In fact, cirrocumulus floccus can form from cirrocumulus castellanus, being the evolutionary state after the base of the original cloud has dissipated.
Cirrocumulus lenticularis is a type of cirrocumulus cloud. The name cirrocumulus lenticularis is derived from Latin, meaning "like a lentil". Cirrocumulus lenticularis are smooth clouds that have the appearance of a lens or an almond. They usually form at the crests of atmospheric waves, which would otherwise be invisible. This species of cirrocumulus can often be quite elongated and normally has very distinguished boundaries. Cirrocumulus lenticularis forms when stable air is forced upward; this is usually due to orographic features, but can occur away from mountains as well. Irisation can occasionally occur with these clouds.
Cirrostratus fibratus or also called Cirrostratus filosus 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. 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.
Cirrostratus nebulosus is a type 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. 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.
A castellanus is a cloud that displays at least in its upper part cumuliform protuberances having the shape of turrets that give a crenellated aspect. Some of these turrets are higher than they are wide; they have a common base and seem to be arranged in a line. The castellanus characteristic is particularly obvious when the clouds are observed from the side.
Stratocumulus floccus is a species of cloud belonging to Stratocumulus cloud genus. Stratocumulus floccus is usually a sign of instability at that altitude. This cloud is usually formed due to the remaining dissipation of a stratocumulus castellanus cloud base.
Stratocumulus castellanus or Stratocumulus castellatus is a type of stratocumulus cloud, castellanus is derived from Latin, meaning 'of a castle' This type of cloud appears as cumuliform turrets vertically rising from a common horizontal cloud base, these turrets are taller than they are wide
