Pyrocumulonimbus
Encyclopedia
The pyrocumulonimbus cloud (pyroCb) 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. According to the American Meteorological Society
’s Glossary of Meteorology, a pyrocumulus is "a cumulus cloud formed by a rising thermal from a fire, or enhanced by buoyant plume emissions from an industrial combustion process." Analogous to the meteorological distinction between cumulus
and cumulonimbus, the pyrocumulonimbus is a fire-aided or –caused convective cloud but with considerable vertical development. The pyroCb reaches the upper troposphere
or even lower stratosphere
and may involve precipitation
(although usually light), hail
, lightning, extreme low-level wind
s, and in some cases even tornado
es . The pyroCb was named following the discovery that extreme manifestations of this pyroconvection caused direct injection of large abundances of smoke into the lower stratosphere
Alternate spellings and abbreviations for pyrocumulonimbus that may be found in the literature include pyro-cumulonimbus, pyro-cb, pyro-Cb and pyrocb. The World Meteorological Organization doesn't recognize pyrocumulonimbus as a distinct cloud type, but classifies it simply as cumulonimbus.
Cumulus cloud
Cumulus 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...
formed above a source of heat such as a wildfire
Wildfire
A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...
and may sometimes even extinguish the fire that formed it. It is the most extreme manifestation of pyrocumulus. According to the American Meteorological Society
American Meteorological Society
The American Meteorological Society promotes the development and dissemination of information and education on the atmospheric and related oceanic and hydrologic sciences and the advancement of their professional applications. Founded in 1919, the American Meteorological Society has a membership...
’s Glossary of Meteorology, a pyrocumulus is "a cumulus cloud formed by a rising thermal from a fire, or enhanced by buoyant plume emissions from an industrial combustion process." Analogous to the meteorological distinction between cumulus
Cumulus cloud
Cumulus 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...
and cumulonimbus, the pyrocumulonimbus is a fire-aided or –caused convective cloud but with considerable vertical development. The pyroCb reaches the upper troposphere
Troposphere
The 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....
or even lower stratosphere
Stratosphere
The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler...
and may involve precipitation
Precipitation (meteorology)
In 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...
(although usually light), hail
Hail
Hail 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...
, lightning, extreme low-level wind
Wind
Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...
s, and in some cases even tornado
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...
es . The pyroCb was named following the discovery that extreme manifestations of this pyroconvection caused direct injection of large abundances of smoke into the lower stratosphere
Alternate spellings and abbreviations for pyrocumulonimbus that may be found in the literature include pyro-cumulonimbus, pyro-cb, pyro-Cb and pyrocb. The World Meteorological Organization doesn't recognize pyrocumulonimbus as a distinct cloud type, but classifies it simply as cumulonimbus.