Pyrocumulonimbus cloud

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Picture of a pyrocumulonimbus cloud, taken from a commercial airliner cruising at about 10 km altitude.

The pyrocumulonimbus cloud (pyroCb) is a type of cumulonimbus cloud that forms 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 a pyrocumulus cloud. 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."[1] Analogous to the meteorological distinction between cumulus and cumulonimbus, the pyrocumulonimbus is a fire-aided or –caused convective cloud, like a pyrocumulus, 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 winds, and in some cases even tornadoes.[2] 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. [3][4] A pyrocumulonimbus may often form from the eruption column of a volcano.

Alternate spellings and abbreviations for pyrocumulonimbus that may be found in the literature include pyro-cumulonimbus, pyro-cb, pyro-Cb and pyrocb.[citation needed] The World Meteorological Organization does not recognize the pyrocumulonimbus as a distinct cloud type, but instead classifies it simply as cumulonimbus.

In 2002, various sensing instruments detected 17 distinct pyrocumulonimbi in North America alone.[5]

2003 Canberra Firestorm[edit]

On the 18 of January 2003, a supercell thunderstorm formed from a pyrocumulonimbus cloud[citation needed] associated with a severe wildfire, during the 2003 Canberra bushfires in Canberra, Australia. The supercell resulted in a huge fire tornado, rated at EF3 on the fujita scale, the first confirmed violent fire tornado.[6][better source needed] The tornado and associated fire killed 4 people and injured 492.

See also[edit]


  1. ^ "AMS Glossary". American Meteorological Society. Retrieved 6 January 2012. 
  2. ^ Fromm, M.; Tupper, A.; Rosenfeld, D.; Servranckx, R.; McRae, R. (2006). "Violent pyro-convective storm devastates Australia's capital and pollutes the stratosphere". Geophysical Research Letters 33 (5). Bibcode:2006GeoRL..33.5815F. doi:10.1029/2005GL025161.  edit
  3. ^ Fromm, M.; Alfred, J.; Hoppel, K.; Hornstein, J.; Bevilacqua, R.; Shettle, E.; Servranckx, R.; Li, Z.; Stocks, B. (2000). "Observations of boreal forest fire smoke in the stratosphere by POAM III, SAGE II, and lidar in 1998". Geophysical Research Letters 27 (9): 1407. Bibcode:2000GeoRL..27.1407F. doi:10.1029/1999GL011200.  edit
  4. ^ Fromm, M.; Servranckx, R. (2003). "Transport of forest fire smoke above the tropopause by supercell convection". Geophysical Research Letters 30 (10). Bibcode:2003GeoRL..30j..49F. doi:10.1029/2002GL016820.  edit
  5. ^ Fire-Breathing Storm Systems
  6. ^ Anja Taylor (6 June 2013). "Fire Tornado". Australian Broadcasting Corporation. Retrieved 6 June 2013.