Cirrus spissatus, also called cirrus densus or cirrus nothus, is the highest of the main

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 ...

genera, and may sometimes even occur in the lower

stratosphere The stratosphere () is the second-lowest layer of the atmosphere of Earth, located above the troposphere and below the mesosphere. The stratosphere is composed of stratified temperature zones, with the warmer layers of air located higher ...

. The characteristic features of

cirrus cloud Cirrus ( cloud classification symbol: Ci) is a genus of high cloud made of ice crystals. Cirrus clouds typically appear delicate and wispy with white strands. In the Earth's atmosphere, cirrus are usually formed when warm, dry air rises, causing ...

s are fine threads or wisps of

ice crystal Ice crystals are solid water (known as ice) in symmetrical shapes including hexagonal columns, hexagonal plates, and dendritic crystals. Ice crystals are responsible for various atmospheric optical displays and cloud formations. Formation ...

s, generally white, but appearing grey when dense and seen against the light. No

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 ...

from this

cloud species Cloud species are a set of fourteen terms used to describe the shape and structure of clouds. Each one has its name abbreviated to a three letter term. References See also

* List of cloud types Cloud types pl:Chmura#Klasyfikacja ch ...

reaches the ground. It also frequently exhibits

optical phenomena Optical phenomena are any observable events that result from the interaction of light and matter. All optics, optical phenomena coincide with Quantum mechanics, quantum phenomena. Common optical phenomena are often due to the interaction of ligh ...

. Cirrus spissatus is the dense cirrus that will partly or completely obscure the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

(or

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

), appearing dark grey when seen

against the light ''Against the Light'' () is the ninth studio album by Singaporean singer Stefanie Sun. It was released on 22 March 2007, by Capitol Music Taiwan, which was under EMI at the time. It is her first and last record to be released under that label. P ...

. Although it arises under various circumstances, it is particularly commonly found in the plumes or anvils of

cumulonimbus cloud Cumulonimbus () is a dense, towering, vertical cloud, typically forming from water vapor condensing in the lower troposphere that builds upward carried by powerful buoyant air currents. Above the lower portions of the cumulonimbus the water ...

s. A different variety of cirrus spissatus also forms from phenomena that have nothing to do with cumulonimbus blow-off or dissipating cumulonimbus cells. When dense cirrus is formed by means other than by cumulonimbus blow-off or dissipating cumulonimbus clouds, it will frequently be seen as many dense patches at different levels (cirrus spissatus duplicatus), often mixed with thin cirrus filaments. Another variety, cirrus spissatus intortus, is sometimes described as looking like "entangled sheaves" of cirrus clouds. When viewed toward the Sun, the denser patches often have gray bases.

References

Sources

* http://www.clouds-online.com/cloud_atlas/cirrus/cirrus.htm * https://web.archive.org/web/20110605020117/http://www.tpub.com/content/aerographer/14269/css/14269_34.htm * http://en.wiktionary.org/wiki/spissus#Latin {{Cloud types Cirrus