Firestorm
A firestorm is a conflagration which attains such intensity that it creates and sustains its own wind system. It is most commonly a natural phenomenon, created during some of the largest bushfires, forest fires, and wildfires. The Black Saturday bushfires, the Great Peshtigo Fire and the Ash Wednesday fires are examples of firestorms, as is that following the 1906 San Francisco Earthquake. Firestorms can also be deliberate effects of targeted explosives such as occurred as a result of the aerial bombings of Hamburg, Dresden, Tokyo, the atomic bombing of Hiroshima.
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[edit] Mechanism
A firestorm is created as a result of the stack effect as the heat of the original fire draws in more and more of the surrounding air. This draft can be quickly increased if a low level jet stream exists over or near the fire. As the updraft mushrooms, strong gusty winds develop around the fire, directed inward which supply the fire with additional air. This would seem to prevent the firestorm from spreading on the wind, but the tremendous turbulence also created causes the strong surface inflow winds to change direction erratically. This wind shear is capable of producing small tornado- or dust devil-like circulations called fire whirls which can also dart around erratically, damage or destroy houses and buildings, and quickly spread the fire to areas outside the central area of the fire. A firestorm may also develop into a mesocyclone and induce true tornadoes.[1] Probably, this is true for the Peshtigo Fire.[2]
The greater draft of a firestorm draws in greater quantities of oxygen, which significantly increases combustion, thereby also substantially increasing the production of heat. The intense heat of a firestorm manifests largely as radiated heat (infrared radiation) which ignites flammable material at a distance ahead of the fire itself. This also serves to expand the area and the intensity of the firestorm. Violent, erratic wind drafts suck movables into the fire, while people and animals caught close or under the fire die for lack of available oxygen.[citation needed] Radiated heat from the fire can melt asphalt, metal, and glass, and turn street tarmac into flammable hot liquid. The very high temperatures replicate the conditions of a smelting furnace,[citation needed] where anything that might possibly burn does so readily, until the firestorm runs out of fuel.
Besides the enormous ash cloud produced by a firestorm, under the right conditions, it can also induce condensation, forming a pyrocumulus cloud or "fire cloud". A large pyrocumulus can grow into a pyrocumulonimbus and produce lightning, which can set off further fires. Apart from forest fires, pyrocumulus clouds can also be produced by volcanic eruptions.
In Australia, the prevalence of eucalyptus trees that have oil in their leaves results in forest fires that are noted for their extremely tall and intense flame front. Hence the bush fires appear more as a firestorm than a simple forest fire. Sometimes, emission of combustible gases from swamps (e.g., methane) has a similar effect. For instance, methane explosions enforced the Peshtigo Fire.[2][3]
[edit] In cities
The same underlying combustion physics can also apply to man-made structures such as cities during war or disaster.
Firestorms are thought to have been part of the mechanism of large urban fires such as the Great Fire of Rome, the Great Fire of London, the 1871 Great Chicago Fire, and the fires resulting from the 1906 San Francisco earthquake and the 1923 Great Kantō earthquake.[citation needed] Firestorms were also created by the firebombing raids of World War II in cities like Hamburg, and Dresden.[4]
| City / Event | Date of the firestorm | Notes |
|---|---|---|
| Great Fire of London[citation needed] | 2 September 1666 – 5 September 1666 | Most of the City of London was destroyed, though few fatalities recorded (this affected a much smaller area than that covered by modern London). |
| 1871 Great Chicago Fire[citation needed] Peshtigo Fire Port Huron Fire |
8 October 1871 | Hundreds killed in Chicago from 8 October to 10 October; up to 2,500 killed in Peshtigo, Wisconsin; others killed in similar fires in Holland and Manistee, Michigan. |
| 1906 San Francisco Earthquake[citation needed] | 18 April 1906 | Also known as the "Ham and Eggs Fire," the fire became uncontrollable because of water mains damaged in the quake. |
| Great Fire of 1910[citation needed] | 20–21 August 1910 | Also known as the "Big Burn" and the "Big Blowup": 87 killed (including one entire Forest Service Fire crew of 28 men), at least 3 towns were partially burned in two days of firestorms; about 3 million acres (12,000 km2) of forest lands in 4 U.S. western states is estimated to have burned. Smoke reached as far as New England and fallout ash was found on snowfields in Greenland.[5] |
| 1923 Great Kantō earthquake[citation needed] | 1 September 1923 | 140,000 dead, most of them in firestorms in Tokyo and the port city of Yokohama. Total damages amounted to 40% of the GNP of that year. |
| Black Friday (1939)[citation needed] | 13 January 1939 | 71 people died, Almost 2,000,000 ha (4,942,000 acres) burnt. Over 1,300 homes,69 sawmills and a total of 3,700 buildings were destroyed. |
| Bombing of Hamburg (Germany)[4] | 27 July 1943 | 46,000 dead.[6] |
| Bombing of Dresden (Germany)[4] | 13 February 1945 | maximum of 25,000 dead.[7] |
| Firebombing of Tokyo (Japan)[citation needed] | 9 March 1945 | ~100,000 dead[citation needed] |
| Firebombing of Kobe (Japan)[citation needed] | 17 March 1945 | 8,841 dead[citation needed] |
| Atomic bombing of Hiroshima (Japan) | 6 August 1945 | Firestorm covering 4.4 square miles (11 km2).[8] The proportion of firestorm victims who survived the initial blast can never be known. |
| Oakland Firestorm of 1991[citation needed] | 20 October 1991 | 25 dead, $1.5 billion in damages[citation needed] |
| Black Saturday bushfires[citation needed] | 7 February 2009 contained 6 March 2009 | 173 people died , 400 individual fires, 450,000 ha (1,100,000 acres) burnt, Over 3,500 structures destroyed[citation needed] |
[edit] Firebombing
Firebombing is a technique designed to damage a target, generally an urban area, through the use of fire, caused by incendiary devices, rather than from the blast effect of large bombs. Such raids often employ both incendiary devices and high explosives. The high explosive destroys roofs making it easier for the incendiary devices to penetrate the structures and cause fires and the high explosives disrupt the ability of firefighters to douse the fires.[4]
Although simple incendiary bombs have been used to destroy buildings since the start of gunpowder warfare, World War II saw the first use of strategic bombing from the air to destroy the ability of the enemy to wage war. London, Coventry and many other British cities were firebombed during the Blitz. Most large German cities were extensively firebombed starting in 1942 and almost all large Japanese cities were firebombed during the last six months of World War II. However as Sir Arthur Harris, the officer commanding RAF Bomber Command from 1942 through to the end of the war in Europe, pointed in his post war analysis, although many attempts were made to create deliberate man made firestorms during World War II few attempts succeed:
The Germans again and again missed their chance, ... of setting our cities ablaze by a concentrated attack. Coventry was adequately concentrated in point of space, but all the same there was little concentration in point of time, and nothing like the fire tornadoes of Hamburg or Dresden ever occurred in this country. But they did do us enough damage to teach us the principle of concentration, the principle of starting so many fires at the same time that no fire fighting services, however efficiently and quickly they were reinforced by the fire brigades of other towns could get them under control.
[edit] See also
[edit] Notes
- ^ Weaver Biko.
- ^ a b Gess & Lutz 2003, p. [page needed]
- ^ Kartman & Brown 1971, p. 48.
- ^ a b c d e Harris 2005, p. 83
- ^ Pyne 2001, p. [page needed].
- ^ Frankland & Webster 1961, pp. 260–261.
- ^ Neutzner 2010, p. 70.
- ^ McRaney & McGahan 1980, p. 24.
[edit] References
- Gess, Denise; Lutz, William (2003) [2002], Firestorm at Peshtigo: A Town, Its People, and the Deadliest Fire in American History, ISBN 9780805072938
- Frankland, Noble; Webster, Charles (1961), The Strategic Air Offensive Against Germany, 1939-1945, Volume II: Endeavour, Part 4, London: Her Majesty's Stationary Office, pp. 260–261
- Harris, Arthur (2005), Bomber Offensive (First, Collins 1947 ed.), Pen & Sword military classics, p. 83, ISBN 1-84415-210-3
- Kartman, Ben; Brown, Leonard (1971), Disaster!, Essay Index Reprint Series, Ayer Publishing, p. 48, ISBN 9780836922806
- McRaney, W.; McGahan, J. (6 August 1980), Radiation dos reconstruction U.S. occupation forces in Hiroshima and Nagasaki, Japan, 1945–1946 (DNA 5512F) — Final Report for Period 7 March 1980-6 August 1980, Science Applications, Inc, p. 24, archived from the original on June 24, 2006, http://web.archive.org/web/20060624185903/http://www.dtra.mil/toolbox/directorates/td/programs/nuclear_personnel/docs/DNATR805512F.pdf
- Neutzner, Matthias; et all (2010), Abschlussbericht der Historikerkommission zu den Luftangriffen auf Dresden zwischen dem 13. und 15. Februar 1945, Landeshauptstadt Dresden, p. 70, http://www.dresden.de/media/pdf/infoblaetter/Historikerkommission_Dresden1945_Abschlussbericht_V1_14a.pdf, retrieved 7 June 2011
- Pyne, Stephen J. (2001), Year of the Fires: The Story of the Great Fires of 1910, Viking-Penguin Press, ISBN 0-670-89990-9
- Weaver, John; Biko, Dan, Firestone Induced Tornado, http://rammb.cira.colostate.edu/visit/fire/video/fire_tornado.html, retrieved February 2012
