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Cirrostratus () is a high-altitude, very thin, and generally uniform stratiform genus-type of 
Cirrostratus clouds sometimes signal the approach of a
cloud
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 ...
. It is composed of ice crystals, which are particles of frozen water
Ice is water that is frozen into a solid state, typically forming at or below temperatures of 0 ° C, 32 ° F, or 273.15 K. It occurs naturally on Earth, on other planets, in Oort cloud objects, and as interstellar ice. As a naturally occ ...
. Cirrostratus is difficult to see and can produce halos. These optical effects are caused 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 frontal system, the cirrostratus often begins as nebulous and turns to fibratus. If the cirrostratus begins as fragmented of clouds in the sky it often means the front is weak. Cirrostratus usually lies above . Its presence indicates a large amount of moisture
Moisture is the presence of a liquid, especially water, often in trace amounts. Moisture is defined as water in the adsorbed or absorbed phase. Small amounts of water may be found, for example, in the air (humidity), in foods, and in some comme ...
in the upper troposphere
The troposphere is the lowest layer of the atmosphere of Earth. It contains 80% of the total mass of the Atmosphere, planetary atmosphere and 99% of the total mass of water vapor and aerosols, and is where most weather phenomena occur. From the ...
.
Clouds resembling cirrostratus occasionally form in the lower stratosphere over the polar regions of Earth
The polar regions, also called the frigid zones or polar zones, of Earth are Earth's polar ice caps, the regions of the planet that surround its geographical poles (the North and South Poles), lying within the polar circles. These high latitud ...
. Polar stratospheric clouds can take on this appearance when composed of tiny supercooled
Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid below its freezing point without it becoming a solid. Per the established international definition, supercooling means ''‘cooling a substance be ...
droplets of water or nitric acid
Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...
.
Cirrostratus clouds sometimes signal the approach of a warm front
Warm, WARM, or Warmth may refer to:
* A somewhat high temperature; heat
* Kindness
Music Albums
* ''Warm'' (Herb Alpert album), 1969
* ''Warm'' (Jeff Tweedy album), 2018
* ''Warm'' (Johnny Mathis album), 1958, and the title song
* ''Warm'' ( ...
if they form after cirrus and spread from one area across the sky, and thus may be signs that precipitation
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...
might follow within the next 12–24 hours, or as soon as 6–8 hours if the front moves fast. 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 (meaning drizzle
Drizzle is a light precipitation which consists of liquid water drops that are smaller than those of rain – generally smaller than in diameter. Drizzle is normally produced by low stratiform clouds and stratocumulus clouds. Precipitation r ...
or snow grains
Snow grains are a form of precipitation. Snow grains are characterized as very small (<1 mm), white, opaque grains of ice that are fairly flat or elongated.
Unlike Cumulus humilis or 
:* Species: Cirrostratus ''fibratus'' (Cs fib) is a high fibrous sheet similar to cirrus but with less detached semi-merged filaments. It is reported in the SYNOP code as CH8 or as CH5 or 6 (depending on the amount of sky covered) 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'' (Cs neb) 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 cirriform top of a mature thundercloud spreads and flattens sufficiently to become a high stratiform cloud.
:::* Mutatus mother clouds: Cirrostratus fibratus ''cirromutatus'' or ''cirrocumulomutatus'' are the result of a complete transformation from cirrus and cirrocumulus genus types. Cirrostratus nebulosis ''altostratomutatus'' results when a high grey nebulous altostratus layer thins out into a whitish layer of featureless high cloud.
stratocumulus
A stratocumulus cloud, occasionally called a cumulostratus, belongs to a genus-type of clouds characterized by large dark, rounded masses, usually in groups, lines, or waves, the individual elements being larger than those in altocumulus, and the ...
clouds are often found below cirrostratus formations, due to the stable air associated with cirrostratus creating an inversion and restricting convection, causing cumuliform clouds to become flattened. Contrail
Contrails (; short for "condensation trails") or vapour trails are line-shaped clouds produced by aircraft engine exhaust or changes in air pressure, typically at aircraft cruising altitudes several kilometres/miles above the Earth's surface. ...
s 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
Haze is traditionally an atmospheric phenomenon in which dust, smoke, and other dry particulates suspended in air obscure visibility and the clarity of the sky. The World Meteorological Organization manual of codes includes a classificati ...
or light mist
Mist is a phenomenon caused by small droplets of water suspended in the cold air, usually by condensation. Physically, it is an example of a Dispersion (chemistry), dispersion. It is most commonly seen where water vapor in warm, moist air meets ...
, used to refer to the milky appearance of the sky when cirrostratus is present.
:* Species: Cirrostratus ''fibratus'' (Cs fib) is a high fibrous sheet similar to cirrus but with less detached semi-merged filaments. It is reported in the SYNOP code as CH8 or as CH5 or 6 (depending on the amount of sky covered) 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'' (Cs neb) 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 cirriform top of a mature thundercloud spreads and flattens sufficiently to become a high stratiform cloud.
:::* Mutatus mother clouds: Cirrostratus fibratus ''cirromutatus'' or ''cirrocumulomutatus'' are the result of a complete transformation from cirrus and cirrocumulus genus types. Cirrostratus nebulosis ''altostratomutatus'' results when a high grey nebulous altostratus layer thins out into a whitish layer of featureless high cloud.
See also
*Stratus cloud
Stratus clouds are low-level clouds characterized by horizontal layering with a uniform base, as opposed to convective or cumuliform clouds formed by rising thermals. The term ''stratus'' describes flat, hazy, featureless clouds at low altit ...
* Altostratus cloud
Altostratus is a middle-altitude cloud genus made up of water droplets, ice crystals, or a mixture of the two. Altostratus clouds are formed when large masses of warm, moist air rise, causing water vapor to condense. Altostratus clouds are usuall ...
* Nimbostratus cloud
A nimbostratus cloud is a multilevel, amorphous, nearly uniform, and often dark-grey cloud that usually produces continuous rain, snow, or sleet, but no lightning or thunder.Cirrostratus nebulosus
* Altostratus undulatus cloud
*
International Cloud Atlas – Cirrostratus
{{DEFAULTSORT:Cirrostratus Cloud Cirrus Stratus
Fractus cloud
Fractus clouds, also called fractostratus or fractocumulus, are small, ragged cloud fragments that are usually found under an ambient cloud base. They form or have broken off from a larger cloud, and are generally sheared by strong winds, givin ...
References
External links
International Cloud Atlas – Cirrostratus
{{DEFAULTSORT:Cirrostratus Cloud Cirrus Stratus