Cumulonimbus (from
Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
''cumulus'', "heaped" and ''nimbus'', "rainstorm") is a dense, towering vertical
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 co ...
,
typically forming from
water vapor
(99.9839 °C)
, -
, Boiling point
,
, -
, specific gas constant
, 461.5 J/( kg·K)
, -
, Heat of vaporization
, 2.27 MJ/kg
, -
, Heat capacity
, 1.864 kJ/(kg·K)
Water vapor, water vapour or aqueous vapor is the gaseous pha ...
condensing in the lower
troposphere
The troposphere is the first and lowest layer of the atmosphere of the Earth, and contains 75% of the total mass of the planetary atmosphere, 99% of the total mass of water vapour and aerosols, and is where most weather phenomena occur. From ...
that builds upward carried by powerful
buoyant air currents. Above the lower portions of the cumulonimbus the water vapor becomes
ice crystal
Ice crystals are solid ice exhibiting atomic ordering on various length scales and include hexagonal columns, hexagonal plates, dendritic crystals, and diamond dust.
Formation
The hugely symmetric shapes are due to depositional growth, na ...
s, such as
snow
Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes.
It consists of frozen crystalline water throughout ...
and
graupel
Graupel (; ), also called soft hail, hominy snow, or snow pellets, is precipitation that forms when supercooled water droplets in air are collected and freeze on falling snowflakes, forming balls of crisp, opaque rime.
Graupel is distinct from ...
, the interaction of which can lead to
hail
Hail is a form of solid precipitation. It is distinct from ice pellets (American English "sleet"), though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailstone. Ice pellets generally fal ...
and to
lightning
Lightning is a naturally occurring electrostatic discharge during which two electric charge, electrically charged regions, both in the atmosphere or with one on the land, ground, temporarily neutralize themselves, causing the instantaneous ...
formation, respectively. When occurring as a
thunderstorm
A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are someti ...
these clouds may be referred to as thunderheads. Cumulonimbus can form alone, in clusters, or along
squall lines. These clouds are capable of producing lightning and other dangerous
severe weather, such as
tornado
A tornado is a violently rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone, altho ...
es, hazardous
wind
Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hou ...
s, and large hailstones. Cumulonimbus progress from overdeveloped
cumulus congestus cloud
Cumulus congestus clouds, also known as towering cumulus, are a form of cumulus that can be based in the low or middle height ranges. They achieve considerable vertical development in areas of deep, moist convection. They are an intermediate stage ...
s and may further develop as part of a
supercell. Cumulonimbus is abbreviated Cb.
Appearance
Towering cumulonimbus clouds are typically accompanied by smaller
cumulus clouds. The cumulonimbus
base may extend several kilometres (miles) across, or be as small as several tens of metres (yards) across, and occupy low to upper altitudes within the troposphere - formed at altitude from approximately . Peaks typically reach to as much as , with extreme instances as high as or more. Well-developed cumulonimbus clouds are characterized by a flat,
anvil
An anvil is a metalworking tool consisting of a large block of metal (usually forged or cast steel), with a flattened top surface, upon which another object is struck (or "worked").
Anvils are as massive as practical, because the higher th ...
-like top (anvil dome), caused by
wind shear or
inversion
Inversion or inversions may refer to:
Arts
* , a French gay magazine (1924/1925)
* ''Inversion'' (artwork), a 2005 temporary sculpture in Houston, Texas
* Inversion (music), a term with various meanings in music theory and musical set theory
* ...
at the
equilibrium level In meteorology, the equilibrium level (EL), or level of neutral buoyancy (LNB), or limit of convection (LOC), is the height at which a rising parcel of air is at the same temperature as its environment.
This means that unstable air is now stable ...
near the
tropopause. The shelf of the anvil may precede the main cloud's vertical component for many kilometres (miles), and be accompanied by lightning. Occasionally, rising air parcels surpass the equilibrium level (due to momentum) and form an
overshooting top culminating at the
maximum parcel level The maximum parcel level (MPL) is the highest level in the atmosphere that a moist convectively rising air parcel will reach after ascending from the level of free convection (LFC) through the free convective layer (FCL) and reaching the equilibriu ...
. 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.
Species
*
Cumulonimbus calvus: cloud with puffy top, similar to cumulus congestus which it develops from; under the correct conditions it can become a cumulonimbus capillatus.
*
Cumulonimbus capillatus: cloud with cirrus-like, fibrous-edged top.
File:Wagga-Cumulonimbus.jpg, Cumulonimbus calvus
Storm cloud.jpg, A clearly developed cumulonimbus fibrous-edged top capillatus
File:Cloudwithlightning.jpg, A freeze-frame of a Cumulonimbus cloud in the distance exposing a flash of lightning
Types
*
Cumulonimbus flammagenitus
The cumulonimbus flammagenitus cloud (CbFg), also known as the pyrocumulonimbus cloud, is a type of cumulonimbus cloud that forms above a source of heat, such as a wildfire or volcanic eruption, and may sometimes even extinguish the fire that ...
(pyrocumulonimbus): rapidly growing cloud forming from non-atmospheric heat and condensation nuclei sources such
wildfire
A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of Combustibility and flammability, combustible vegetation. Depending on the type of vegetation present, a wildfire ...
s and
volcanic eruption
Several types of volcanic eruptions—during which lava, tephra (ash, lapilli, volcanic bombs and volcanic blocks), and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often ...
s.
Supplementary features
Accessory clouds
*
Arcus
Arcus may refer to:
Businesses and organizations
*ARCUS, the Arctic Research Consortium of the United States, supporting Arctic policy in the U.S.
*Arcus AS, a Norwegian producer of liquor
* Arcus Co., a Bulgarian firearm manufacturer
*Arcus Fou ...
(including
roll
Roll or Rolls may refer to:
Movement about the longitudinal axis
* Roll angle (or roll rotation), one of the 3 angular degrees of freedom of any stiff body (for example a vehicle), describing motion about the longitudinal axis
** Roll (aviation), ...
and
shelf
Shelf ( : shelves) may refer to:
* Shelf (storage), a flat horizontal surface used for display and storage
Geology
* Continental shelf, the extended perimeter of a continent, usually covered by shallow seas
* Ice shelf, a thick platform of ice f ...
clouds): low, horizontal cloud formation associated with the leading edge of thunderstorm
outflow
Outflow may refer to:
*Capital outflow, the capital leaving a particular economy
*Bipolar outflow, in astronomy, two continuous flows of gas from the poles of a star
*Outflow (hydrology), the discharge of a lake or other reservoir system
* Outflow ...
.
*
Pannus
Pannus is an abnormal layer of fibrovascular tissue or granulation tissue. Common sites for pannus formation include over the cornea, over a joint surface (as seen in rheumatoid arthritis), or on a prosthetic heart valve. Pannus may grow in a tu ...
: accompanied by a lower layer of fractus species cloud forming in precipitation.
*
Pileus (species calvus only): small cap-like cloud over parent cumulonimbus.
*
Velum
Velum may refer to:
Human anatomy
* Superior medullary velum, anterior medullary velum or valve of Vieussens, white matter, in the brain, which stretches between the superior cerebellar peduncles
** Frenulum of superior medullary velum, a sligh ...
: a thin horizontal sheet that forms around the middle of a cumulonimbus.
Supplementary features
*
Incus
The ''incus'' (plural incudes) or anvil is a bone in the middle ear. The anvil-shaped small bone is one of three ossicles in the middle ear. The ''incus'' receives vibrations from the ''malleus'', to which it is connected laterally, and transmit ...
(species capillatus only): cumulonimbus with flat anvil-like cirriform top caused by wind shear where the rising air currents hit the
inversion
Inversion or inversions may refer to:
Arts
* , a French gay magazine (1924/1925)
* ''Inversion'' (artwork), a 2005 temporary sculpture in Houston, Texas
* Inversion (music), a term with various meanings in music theory and musical set theory
* ...
layer at the tropopause.
* Mamma or
mammatus
Mammatus (also called mamma or mammatocumulus, meaning "mammary cloud") is a cellular pattern of pouches hanging underneath the base of a cloud, typically a cumulonimbus raincloud, although they may be attached to other classes of parent cloud ...
: 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 drop very low, sometimes just above ground level.
*
Flanking line is a line of small cumulonimbus or cumulus generally associated with severe thunderstorms.
* An
overshooting top is a dome that rises above the thunderstorm; it is associated with severe weather.
Precipitation-based supplementary features
*
Rain
Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water f ...
: precipitation that reaches the ground as liquid, often in a
precipitation shaft.
*
Virga: precipitation that evaporates before reaching the ground.
File:Rolling-thunder-cloud.jpg, Arcus cloud (shelf cloud) leading a thunderstorm
File:Cumulus pileus.jpg, A cap (pileus) atop a congestus
File:Fly00890 - Flickr - NOAA Photo Library.jpg, Incus with a velum edge
File:Mammatus clouds regina sk june 2012.JPG, Mammatocumulus with drooping pouches
File:Cumulonimbus tuba.jpg, A funnel cloud (tuba) over the Netherlands
File:Anvil shaped cumulus panorama edit.jpg, Flanking line in front of a strong thunderstorm
File:Cumulonimbus13 - NOAA.jpg, An overshooting top is a dome of clouds atop a cumulonimbus
File:Sunnystormcloud.jpg, Cumulonimbus calvus against sunlight with rain falling beneath it as a rain shaft
A precipitation shaft is a weather phenomenon, visible from the ground at large distances from the storm system, as a dark vertical shaft of heavy rain, hail, or snow, generally localized over a relatively small area.
This is different from a v ...
.
File:Cb virga 1.JPG, Rain evaporating before reaching the ground (virga)
Effects
Cumulonimbus storm cells can produce torrential
rain
Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water f ...
of a
convective
Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convect ...
nature (often in the form of a
rain shaft
A precipitation shaft is a weather phenomenon, visible from the ground at large distances from the storm system, as a dark vertical shaft of heavy rain, hail, or snow, generally localized over a relatively small area.
This is different from a v ...
) and
flash flood
A flash flood is a rapid flooding of low-lying areas: washes, rivers, dry lakes and depressions. It may be caused by heavy rain associated with a severe thunderstorm, hurricane, or tropical storm, or by meltwater from ice or snow flowing o ...
ing, as well as
straight-line winds. Most storm cells die after about 20 minutes, when the
precipitation
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...
causes more
downdraft than
updraft, causing the energy to dissipate. If there is sufficient instability and moisture in the
atmosphere
An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...
, however (on a hot summer day, for example), the
outflowing moisture and
gusts from one storm cell can lead to new cells forming just a few kilometres (miles) from the former one a few tens of minutes later or in some cases hundreds of kilometres (miles) away many hours later. This process cause thunderstorm formation (and decay) to last for several hours or even over multiple days. Cumulonimbus clouds can also occur as a dangerous winter storms called "
thundersnow" which are associated with particularly intense snowfall rates and with
blizzard conditions when accompanied by strong winds that further reduce
visibility
The visibility is the measure of the distance at which an object or light can be clearly discerned. In meteorology it depends on the transparency of the surrounding air and as such, it is unchanging no matter the ambient light level or time of ...
. However, cumulonimbus clouds are most common in
tropical
The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in
the Southern Hemisphere at S. The tropics are also referred to ...
regions and are also frequent in moist environments during the warm season in the
middle latitudes
The middle latitudes (also called the mid-latitudes, sometimes midlatitudes, or moderate latitudes) are a spatial region on Earth located between the Tropic of Cancer (latitudes 23°26'22") to the Arctic Circle (66°33'39"), and Tropic of Caprico ...
.
A
dust storm
A dust storm, also called a sandstorm, is a meteorological phenomenon common in arid and semi-arid regions. Dust storms arise when a gust front or other strong wind blows loose sand and dirt from a dry surface. Fine particles are transporte ...
caused by a cumulonimbus downburst is a
haboob
A haboob ( ar, هَبوب, lit=blasting/drifting, translit=habūb) is a type of intense dust storm carried on an atmospheric gravity current, also known as a weather front. Haboobs occur regularly in dry land area regions throughout the world.
...
.
Hazards to aviation
Cumulonimbus are a notable
hazard to aviation due most importantly to potent wind currents but also reduced visibility and lightning, as well as
icing and hail if flying inside the cloud. Within and in the vicinity of thunderstorms there is significant
turbulence
In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between ...
and
clear-air turbulence (particularly
downwind), respectively. Wind shear within and under a cumulonimbus is often intense with
downbursts being responsible for many accidents in earlier decades before training and technological
detection and
nowcasting measures were implemented. A small form of downburst, the microburst, is the most often implicated in crashes because of their rapid onset and swift changes in wind and aerodynamic conditions over short distances. Most downbursts are associated with visible precipitation shafts, however, dry microbursts are generally invisible to the naked eye. At least one fatal commercial airline
accident was associated with flying through a tornado.
Life cycle or stages
In general, cumulonimbus require moisture, an
unstable air mass, and a lifting force in order to form. Cumulonimbus typically go through three stages: the developing stage, the mature stage (where the main cloud may reach supercell status in favorable conditions), and the dissipation stage.
The average thunderstorm has a diameter and a height of approximately . Depending on the conditions present in the atmosphere, these three stages take an average of 30 minutes to go through.
Cloud types
Clouds form when the
dew point
The dew point is the temperature to which air must be cooled to become saturated with water vapor, assuming constant air pressure and water content. When cooled below the dew point, moisture capacity is reduced and airborne water vapor will cond ...
temperature of water is reached in the presence of
condensation nuclei
Cloud condensation nuclei (CCNs), also known as cloud seeds, are small particles typically 0.2 µm, or one hundredth the size of a cloud droplet. CCNs are a unique subset of aerosols in the atmosphere on which water vapour condenses. This ca ...
in the troposphere. The atmosphere is a dynamic system, and the local conditions of turbulence,
uplift
Uplift may refer to: Science
* Geologic uplift, a geological process
** Tectonic uplift, a geological process
* Stellar uplift, the theoretical prospect of moving a stellar mass
* Uplift mountains
* Llano Uplift
* Nemaha Uplift
Business
* Uplif ...
, and other parameters give rise to many types of clouds. Various types of cloud occur frequently enough to have been categorized. Furthermore, some atmospheric processes can make the clouds organize in distinct patterns such as
wave cloud
A wave cloud is a cloud form created by atmospheric internal waves.
Formation
The atmospheric internal waves that form wave clouds are created as stable air flows over a raised land feature such as a mountain range, and can form either direc ...
s or
actinoform cloud
An actinoform or actiniform describes a collection of marine low clouds that takes a distinct shape. They are named after the Greek language, Greek word for "ray" due to their radial structure. Actinoform clouds can spread out over across and th ...
s. These are large-scale structures and are not always readily identifiable from a single point of view.
See also
*
Atmospheric convection
*
Atmospheric thermodynamics Atmospheric thermodynamics is the study of heat-to-work transformations (and their reverse) that take place in the earth's atmosphere and manifest as weather or climate. Atmospheric thermodynamics use the laws of classical thermodynamics, to descr ...
*
Convective instability
*
Hot tower
*
Lifted condensation level (LCL),
convective condensation level The convective condensation level (CCL) represents the height (or pressure) where an air parcel becomes saturated when heated from below and lifted adiabatically due to buoyancy.
In the atmosphere, assuming a constant water vapor mixing ratio, the ...
(CCL),
level of free convection (LFC), and
free convective layer (FCL)
*
William Rankin
Lieutenant Colonel William Henry Rankin (October 16, 1920 – July 6, 2009) was one of only two known persons to survive a fall from the top of a cumulonimbus thunderstorm cloud; the other was Ewa Wiśnierska. He was a pilot in the United State ...
*
Ewa Wiśnierska
Ewa Wiśnierska, née Cieślewicz (born 23 December 1971, Nysa, Poland, Nysa, Poland), is a German paragliding, paraglider, a member of the German national paragliding team, who won the Paragliding World Cup on several occasions. She is mostly know ...
References
External links
Clouds-Online.com Cloud Atlas with many photos and description of the different cloud generaMetOffice.gov.uk Learn about thunderstorms and how cumulonimbus clouds form
{{DEFAULTSORT:Cumulonimbus Cloud
Cirrus
Cumulus
Severe weather and convection