Jump to content

Firestorm

From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by 123lilbrad (talk | contribs) at 01:11, 7 August 2012 (→‎City firestorms/Destroyed City). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

This article is about fires. For other uses, see Firestorm (disambiguation).

A firestorm during the 1988 Yellowstone fires

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 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, and the atomic bombing of Hiroshima.

Mechanism

See also: Thermal column
Firestorm: fire (1), updraft (2), strong gusty winds (3)

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. Radiated heat from the fire can melt asphalt, metal, and glass, and turn street tarmac into flammable hot liquid. The very high temperatures ignite anything that might possibly burn, 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]

City firestorms

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]

In contrast, experts suggest that due to the nature of modern US city design and construction a raging firestorm is unlikely there.[5]

City / Event Date of the firestorm Notes
Bombing of Hamburg (Germany)[4] 27 July 1943 46,000 dead.[6] A firestorm area of

approximately 4.5 square miles (12 km2) was reported at Hamburg.[7]

Bombing of Dresden (Germany)[4] 13 February 1945 maximum of 25,000 dead.[8] A firestorm area of

approximately 8 square miles (21 km2) was reported at Dresden.[7]

Firebombing of Tokyo (Japan) 9–10 March 1945 Firestorm covering 16 square miles (41 km2). 267,171 buildings destroyed, 83,793 dead.[9] The most devastating air raid in history with destruction greater than the Atomic bombing of Hiroshima, although with fewer casualties.[9] Despite Tokyo commonly being assumed to be a firestorm event, it is more accurately termed an area fire conflagration and not a true fire storm, due to the high ambient surface wind speed at the time of the firebombing in Tokyo preventing a true firestorm from forming. Instead the fire was fanned by winds and grew over a large area, strong surface winds cause flames to slant forward, and fire to spread in the direction of the wind. Since fire storms are characterized by little outward spread, it is clear that, in the general case fire storms will not develop in the presence of ground winds strong enough to spread the fire to an appreciable extent.[10]
Bombing of Kassel in World War II 22 October 1943 9,000 dead. 24,000 Dwellings destroyed. Area burned 23 square miles (60 km2); the percentage of this area which was destroyed by conventional conflagration and that destroyed by firestorm is unspecified.[11] Although a much larger area was destroyed by fire in Kassel than even Tokyo and Hamburg, the city fire caused a smaller less extensive firestorm than that at Hamburg.[12]
Bombing of Darmstadt in World War II 11 September 1944 8,000 dead. Area destroyed by fire 4 square miles (10 km2), again the percentage of this which was done by firestorm remains unspecified. 20,000 dwellings destroyed.[11]
Bombing of Ube, Yamaguchiin World War II A momentary fire storm of about 0.5 square miles (1.3 km2) was reported at Ube, Japan.[7] The reports that the Ube bombing produced a firestorm, along with computer modelling, has set one of the four physical conditions which a fire must meet to develop into a true firestorm. The size of the Ube firestorm is regarded as the lower size limit of a firestorm. Glasstone and Dolan:

The minimum requirements for a fire storm to develop: no.4 A minimum burning area of about 0.5 square miles (1.3 km2).

— Glasstone and Dolan (1977).[13]
Atomic bombing of Hiroshima (Japan) 6 August 1945 Firestorm covering 4.4 square miles (11 km2).[14] No estimate can be given of the number of fire deaths, since the fire area was largely within the blast damage region.[15]

Firebombing

Braunschweig burning after aerial firebombing attack in 1944.

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. The high explosives also disrupt the ability of firefighters to douse the fires.[4]

Although 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. 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."

— Arthur Harris, [4]

According to physicist David Hafemeister firestorms occurred after about 5% of all fire-bombing raids during World War II (but he does not explain if this is a percentage based on both Allied and Axis raids, or combined Allied raids, or U.S. raids alone).[16] In 2005 The American National Fire Protection Association stated in a report that there were 3 major fire storms resulting from Allied conventional bombing campaigns during World War II: Hamburg, Dresden and Tokyo.[17] They do not include the comparatively minor firestorms at Kassel, Darmstadt or even Ube into their major firestorm category. Despite later quoting Glasstone and Dolan and data collected from these smaller firestorms:

based on World War II experience with mass fires resulting from air raids on Germany and Japan, the minimum requirements for a fire storm to develop are considered by some authorities to be the following: (1) at least 8 pounds of combustibles per square foot of fire area, (2) at least half of the structures in the area on fire simultaneously, (3) a wind of less than 8 miles per hour at the time, and (4) a minimum burning area of about half a square mile.

— Glasstone and Dolan (1977).[18]

Evil Tower DEEAILBEE Downtown Destroyes By 4/10 Dragon Downtown D.D April 10 2012

Deaths City Money Homes Town Road survival gear Fire giant Crystal Electronic
$1 $1.99 N/A $6.000 $7.00 $1.00 N/A $2.000 N/A N/A
$7.61 $1.05 N/A $8.000 $40.000 $8.000 N/A $8.00 $5.999 N/A
$10.00 $4.000 N/A $4.000 $30.888 $5.00 N/A $1.000 N/A N/A
$1.42 $1.00 N/A $1.000 $50.000 $6.00 N/A $4.00 N/A N/A
$1.99 $7.000 N/A $3.00 $7.000 $90.000 N/A $5.000.000 N/A N/A
$5.99 $100.000 N/A $4.99 $8.00 $5.00 N/A $300.000 N/A N/A
$8.99 $2.00 N/A $7.000 $6.91 $5.000 N/A $1.00 N/A N/A
$1.200 $599.00 N/A 6.00 $7.177 $7.000.000 N/A $1.00 N/A N/A

DSC MONEY

See also

Notes

  1. ^ Weaver & Biko.
  2. ^ a b Gess & Lutz 2003, p. [page needed]
  3. ^ Kartman & Brown 1971, p. 48.
  4. ^ a b c d e Harris 2005, p. 83
  5. ^ http://hps.org/hsc/documents/Planning_Guidance_for_Response_to_a_Nuclear_Detonation-2nd_Edition_FINAL.pdf Page 24 of Planning Guidance for response to a nuclear detonation. Written with the collaboration of FEMA & NASA to name a few agencies.
  6. ^ Frankland & Webster 1961, pp. 260–261.
  7. ^ a b c Exploratory analysis of Firestorms. pg 31 http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=AD0616638
  8. ^ Neutzner 2010, p. 70.
  9. ^ a b Michael D. Gordin (2007). Five days in August: how World War II became a nuclear war. Princeton University Press. p. 21. ISBN 0-691-12818-9.
  10. ^ Exploratory analysis of Firestorms. pg 39,40,53 & 54. http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=AD0616638
  11. ^ a b The Cold War Who won? pg 82 to 88 Chapter 18 http://www.scribd.com/doc/49221078/18-Fire-in-WW-II
  12. ^ Royal Air Force Bomber Command http://www.raf.mod.uk/bombercommand/oct43.html
  13. ^ Glasstone & Dolan 1977, pp. 299, 200, ¶ 7.58.
  14. ^ McRaney & McGahan 1980, p. 24.
  15. ^ Exploratory analysis of Firestorms. pg 53 http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=AD0616638
  16. ^ Hafemeister 1991, p. 24 (¶ 2nd to last).
  17. ^ American National Fire Protection Association 2005, p. 24.
  18. ^ Glasstone & Dolan 1977, pp. 299, 300, ¶ 7.58.

References

Retrieved from "https://en.wikipedia.org/w/index.php?title=Firestorm&oldid=506155657"