Cumulonimbus is a towering vertical
cloudA cloud is a visible mass of liquid droplets or frozen crystals made of water and/or various chemicals suspended in the atmosphere above the surface of a planetary body. They are also known as aerosols. Clouds in Earth's atmosphere are studied in the cloud physics branch of meteorology...
(family D2) that is very tall, dense, and involved in
thunderstormA thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...
s and other inclement
weatherWeather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...
. Cumulonimbus originates from
LatinLatin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
: Cumulus "Heap" and nimbus "rain". It is a result of
atmospheric instabilityAtmospheric instability is a condition where the atmosphere is generally considered to be unstable and as a result the weather is subject to a high degree of variability through distance and time...
. These clouds can form alone, in clusters, or along a
cold frontA cold front is defined as the leading edge of a cooler mass of air, replacing a warmer mass of air.-Development of cold front:The cooler and denser air wedges under the less-dense warmer air, lifting it...
in a
squallA squall is a sudden, sharp increase in wind speed which is usually associated with active weather, such as rain showers, thunderstorms, or heavy snow. Squalls refer to an increase in the sustained winds over a short time interval, as there may be higher gusts during a squall event...
line. They create
lightningLightning is an atmospheric electrostatic discharge accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms...
through the heart of the cloud. Cumulonimbus clouds form from
cumulus cloudCumulus clouds are a type of cloud with noticeable vertical development and clearly defined edges. Cumulus means "heap" or "pile" in Latin. They are often described as "puffy" or "cotton-like" in appearance. Cumulus clouds may appear alone, in lines, or in clusters...
s (namely from cumulus congestus) and can further develop into a
supercellA supercell is a thunderstorm that is characterized by the presence of a mesocyclone: a deep, continuously-rotating updraft. For this reason, these storms are sometimes referred to as rotating thunderstorms...
, a severe thunderstorm with special features.
Appearance
The anvil is the flat layer at the top. The downdraft is the rainy area to the right.
Cumulonimbus clouds usually form from cumulus coop at a much lower height, thus making them, like cumulus clouds, grow vertically instead of horizontally, thus giving the cumulonimbus its mushroom shape. The base of a cumulonimbus can be several miles across, and it can be tall enough to occupy middle as well as low
altitudeAltitude or height is defined based on the context in which it is used . As a general definition, altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The reference datum also often varies according to the context...
s; though formed at an altitude of about 500 to 13,000 feet (150 to 3,960 metres), its peak can reach up to 75,000 feet (23,000 metres) in extreme cases. Typically, it peaks at a much lower height, usually up to 20,000 feet (6,090 meters). Well-developed cumulonimbus clouds are also characterized by a flat,
anvilAn anvil is a basic tool, a block with a hard surface on which another object is struck. The inertia of the anvil allows the energy of the striking tool to be transferred to the work piece. In most cases the anvil is used as a forging tool...
-like top (anvil dome), caused by straight line winds at the higher altitudes which shear off the top of the cloud, as well as by an
inversionIn meteorology, an inversion is a deviation from the normal change of an atmospheric property with altitude. It almost always refers to a temperature inversion, i.e...
over the thunderstorm caused by rising temperatures above the
tropopauseThe tropopause is the atmospheric boundary between the troposphere and the stratosphere.-Definition:Going upward from the surface, it is the point where air ceases to cool with height, and becomes almost completely dry...
. This anvil shape can precede the main cloud structure for many miles, causing anvil
lightningLightning is an atmospheric electrostatic discharge accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms...
. This is the largest of clouds usually extending through all three cloud regions when vertically developed. All other clouds are dwarfed even compared to small cumulonimbus clouds.
Species
- Cumulonimbus arcus
An arcus cloud is a low, horizontal cloud formation. Roll clouds and shelf clouds are the two types of arcus clouds. A shelf cloud is usually associated with the leading edge of thunderstorm outflow; roll clouds are usually formed by outflows of cold air from sea breezes or cold fronts in the...
- Cumulonimbus calvus
Cumulonimbus calvus is a moderately tall cumulonimbus cloud which is capable of precipitation, but has not yet reached the height where it forms into a cumulonimbus capillatus or cumulonimbus incus...
: cloud with puffy top, similar to cumulus congestus, but larger;
- Cumulonimbus capillatus: cloud with cirrus-like, fibrous-edged top;
- Cumulonimbus incus
A cumulonimbus incus is a cumulonimbus cloud which has reached the level of stratospheric stability and has formed the characteristic flat, anvil-top shape...
: subtype of Cumulonimbus capillatus, with flat anvil-like top.
- Cumulonimbus mammatus
- Cumulonimbus pannus
Fractus clouds 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, giving them a jagged, shredded appearance. Fractus have irregular patterns, appearing much like torn...
- Cumulonimbus pileus
- Cumulonimbus praecipitatio
- Cumulonimbus tuba
A funnel cloud is a funnel-shaped cloud of condensed water droplets, associated with a rotating column of wind and extending from the base of a cloud but not reaching the ground or a water surface. A funnel cloud is usually visible as a cone-shaped or needle like protuberance from the main cloud...
- Cumulonimbus velum
Cumulonimbus velum is a type of cumulonimbus cloud, identified by its undulating, or sail-like appearance....
- Cumulonimbus virga
Effects
Cumulonimbus storm cells can produce heavy
rainRain is liquid precipitation, as opposed to non-liquid kinds of precipitation such as snow, hail and sleet. Rain requires the presence of a thick layer of the atmosphere to have temperatures above the melting point of water near and above the Earth's surface...
of a
convectiveConvection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....
nature and
flash floodA flash flood is a rapid flooding of geomorphic low-lying areas—washes, rivers, dry lakes and basins. It may be caused by heavy rain associated with a storm, hurricane, or tropical storm or meltwater from ice or snow flowing over ice sheets or snowfields...
ing, as well as straight-line winds. Most storm cells die after about 20 minutes, when the
precipitationIn meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...
causes more downdraft than updraft, causing the energy to dissipate. If there is enough solar energy in the
atmosphereThe atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
, however (on a hot summer's day, for example), the moisture from one storm cell can
evaporateEvaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....
rapidly—resulting in a new cell forming just a few miles from the former one. This can cause thunderstorms to last for several hours. This multicell cloud structure exists until a cold downdraft preceding the cumulonimbus at ground level flows before the cloud at a distance sufficient to disrupt updraft (5–10 kilometers). From this moment on the cumulonimbus cloud quickly degrades and dissipates, forming
cirrus spissatusCirrus spissatus clouds are the highest of the main cloud genera, and may sometimes even occur in the lower stratosphere. The characteristic features of cirrus clouds are fine threads or wisps of ice crystals, generally white, but appearing grey when dense and seen against the light. No...
, dense anvil-like
cirrusCirrus clouds are atmospheric clouds generally characterized by thin, wispy strands, giving them their name from the Latin word cirrus meaning a ringlet or curling lock of hair...
, stratocumulus diurnalis or stratocumulus vesperalis. Cumulonimbus clouds can cause
tornadoA tornado is a violent, dangerous, 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. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider...
es.
Cumulonimbus clouds sometimes form
mammatus cloudMammatus, also known as mammatocumulus , is a meteorological term applied to a cellular pattern of pouches hanging underneath the base of a cloud...
s.
Cumulonimbus clouds contain severe convection currents, with very high, unpredictable winds, particularly in the vertical plane (
updrafts and downdraftsAn updraft or downdraft is the vertical movement of air as a weather related phenomenon. One of two forces causes the air to move. Localized regions of warm or cool air will exhibit vertical movement. A mass of warm air will typically be less dense than the surrounding region, and so will rise...
). They are therefore extremely dangerous to
aircraftAn aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
. Smaller, propeller-driven planes cannot cope with the conditions and must fly around them; larger jet aircraft fly over the smaller ones and around larger examples. Larger planes are also equipped with weather
radarRadar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
and
wind shearWind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and direction over a relatively short distance in the atmosphere...
detectors to help guide them through, in the event that they need to pass through such clouds to land. Snow and ice conditions can develop in the colder upper portions of the clouds, even when the air temperatures at ground level are moderate.
The air convection can also form
mesocycloneA mesocyclone is a vortex of air, approximately 2 to 10 miles in diameter , within a convective storm....
s, which can cause
hailHail is a form of solid precipitation. It consists of balls or irregular lumps of ice, each of which is referred to as a hail stone. Hail stones on Earth consist mostly of water ice and measure between and in diameter, with the larger stones coming from severe thunderstorms...
and tornadoes.
Cloud types
CloudA cloud is a visible mass of liquid droplets or frozen crystals made of water and/or various chemicals suspended in the atmosphere above the surface of a planetary body. They are also known as aerosols. Clouds in Earth's atmosphere are studied in the cloud physics branch of meteorology...
s form when the dewpoint of
waterWater is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
is reached in the presence of condensation nuclei in the
troposphereThe troposphere is the lowest portion of Earth's atmosphere. It contains approximately 80% of the atmosphere's mass and 99% of its water vapor and aerosols....
. The atmosphere is a dynamic system, and the local conditions of
turbulenceIn fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic and stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time...
,
upliftTectonic uplift is a geological process most often caused by plate tectonics which increases elevation. The opposite of uplift is subsidence, which results in a decrease in elevation. Uplift may be orogenic or isostatic.-Orogenic uplift:...
and other parameters give rise to many types of clouds. Various types of clouds occur frequently enough to have been categorized. Furthermore, some atmospheric processes can make the clouds organize in distinct patterns such as "
wave cloudA 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 directly above or in the lee of the feature. As an air mass...
s" or "
actinoform cloudAn actinoform or actiniform cloud is a collection of marine low clouds that takes a distinct shape. They are named after the Greek word for "ray" due to their radial structure. Actinoform clouds can spread out over across and thus cannot be easily seen with the naked eye...
s", these are large-scale structures and not always readily identifiable from single point of view.
See also
- Cumulonimbus calvus
Cumulonimbus calvus is a moderately tall cumulonimbus cloud which is capable of precipitation, but has not yet reached the height where it forms into a cumulonimbus capillatus or cumulonimbus incus...
- Cumulonimbus incus
A cumulonimbus incus is a cumulonimbus cloud which has reached the level of stratospheric stability and has formed the characteristic flat, anvil-top shape...
- Cumulus congestus cloud
- Funnel cloud
A funnel cloud is a funnel-shaped cloud of condensed water droplets, associated with a rotating column of wind and extending from the base of a cloud but not reaching the ground or a water surface. A funnel cloud is usually visible as a cone-shaped or needle like protuberance from the main cloud...
- Hot tower
A hot tower is a tropical cumulonimbus cloud that penetrates the tropopause, i.e. it reaches out of the lowest layer of the atmosphere, the troposphere, into the stratosphere. In the tropics, the tropopause typically lies at least 15 km above sea level...
- Mammatus cloud
Mammatus, also known as mammatocumulus , is a meteorological term applied to a cellular pattern of pouches hanging underneath the base of a cloud...
- Pileus
A pileus , also called scarf cloud or cap cloud, is a small, horizontal cloud that can appear above a cumulus or cumulonimbus cloud, giving the parent cloud a characteristic "hoodlike" appearance. Pilei tend to change shape rapidly. They are formed by strong updrafts acting upon moist air at lower...
- Pyrocumulonimbus
The pyrocumulonimbus cloud is a type of cumulus cloud formed above a source of heat such as a wildfire and may sometimes even extinguish the fire that formed it. It is the most extreme manifestation of pyrocumulus...
- Squall line
A squall line is a line of severe thunderstorms that can form along or ahead of a cold front. In the early 20th century, the term was used as a synonym for cold front. It contains heavy precipitation, hail, frequent lightning, strong straight-line winds, and possibly tornadoes and waterspouts....
- Storm
A storm is any disturbed state of an astronomical body's atmosphere, especially affecting its surface, and strongly implying severe weather...
- Supercell
A supercell is a thunderstorm that is characterized by the presence of a mesocyclone: a deep, continuously-rotating updraft. For this reason, these storms are sometimes referred to as rotating thunderstorms...
- Tornado
A tornado is a violent, dangerous, 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. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider...
External links