Pyrocumulonimbus
Pyrocumulonimbus ( Latin pyro "fire", cumulus "accumulation" and nimbus "rain cloud"), or PyroCb for short, also called cumulonimbus flammageniti , are called special fire clouds by meteorologists , which are formed by the formation of large clouds with smoke , soot and ash . They can transport smoke aerosols into the lower stratosphere , which can spread around the world for months. PyroCbs are basically formed under two conditions
a) if large and intense heat sources have arisen and
b) unstable atmospheric weather conditions prevail over them.
The meteorologist Michael Fromm names three conditions for the formation: hot, dry and windy. Pyrocumulonibi can develop in large forest fires or bush fires . They have been known since 1988, but have not been fully explored.
These clouds of fire can hardly be fought on the ground because they generate such great heat that fire fighters have to retreat and fire fighting from the air is impossible because of the thunderstorms.
Designations
There are several names and spellings for the fire cloud pyrocumulonimbus such as cumulonimbus flammageniti (abbreviation: Cb-Fg, CbFg), pyrocumulonimbus, pyro-cumulonimbus, pyro-cumulonimbus (abbreviation: PyroCb, pyroCb, pyro-Cb),. The term volcanic cumulonimbus is used for clouds ejected from a volcano.
In the media, these PyroCbs are also referred to as "fires that cannot be fought" or "fires that make their own weather". From the NASA , they are called the "fire-breathing dragon of clouds" ( "fire-breathing dragon clouds").
Emergence
Smoke develops over ground fires because they condense the moisture contained in the fuel in plants and the humidity in the atmosphere and ash particles rise with it. The cloud that forms is commonly referred to as a cloud of fire. Large fires on the ground create a cloud of hot, rapidly moving air with smoke that rises quickly and pulls large air masses upwards with an air speed of up to 160 km / h. The air turbulence that arises mixes cool air into the cloud, which further expands and cools as it continues to rise. As you climb up, the air pressure continues to drop and heat is released. This leads to continued condensation, with ice crystals forming. The ice particles rub against the very cold upper parts of these clouds and build up electrical charges, which are released with lightning, creating thunderstorm winds. After a thunderstorm with lightning strikes, the cloud is called pyrocumulonimbus. Lightning bolts were observed that caused further fires 30 kilometers from a PyroCb. PyroCb can rise into the lower stratosphere and usually last as a cloud for one to eight hours.
Discovery story
First observation
It used to be assumed that only medium volcanic eruptions are able to transport aerosols into the lower stratosphere. In the meantime, researchers assume that the largest PyroCbs transport smoke aerosols in the amount of a medium volcanic eruption into the lower stratosphere. PyroCbs arise from natural causes or are caused by humans. It was known that the firestorms transported the ashes produced by the bombing of Hamburg in World War II into the stratosphere.
In 1988 a cloud of fire was observed carrying smoke into the stratosphere and spreading it around the world. This cloud of fire was eponymous with pyrocumuloninimbus. PyroCbs have only been scientifically investigated since 2000.
Examples
Pyrocumulonimbi arise more frequently than is generally known, here are some examples: Through observations, researchers counted 17 PyroCbs in the 2002 fire season in the USA / Canada area. The 2009 Black Saturday bushfire , which was struck by lightning and turned into a PyroCb, burned 70% of the area of the Australian Capital Territory , destroyed 500 homes and killed four people. In Greece, PyroCbs were created in 2007 and 2009, respectively. PyroCb rose in 2019 in Bolivia, Russia, and North America. In the course of the Black Saturday bushfire in February 2009 in Victoria , Australia , three PyroCbs formed simultaneously, which rose to a height of up to 15 kilometers. 173 people lost their lives in this bush fire. Due to the findings on PyroCbs year was 2016, the mushroom cloud , which after the explosion of the atomic bomb on Hiroshima made, based on recognized as PyroCb of photographs from the year 1946th The realization was: It was not the atomic explosion that caused the cloud of fire, but the heat of the fire on the ground. During forest fires in the Canadian province of British Columbia in August 2017 , a PyroCb was produced that rose twelve kilometers and then two months later to 23 kilometers. PyroCbs have also existed in Spain, Portugal and Sweden. Experts also anticipate that such clouds of smoke will also occur in Central and Northern Europe. In the 2019/2020 bushfires in Australia , a PyroCb was formed during the three months of the Gospers Mountain bushfire north of Sydney in the state of New South Wales .
Fire fighting
After this type of fire cloud has formed, firefighters must retreat on the ground and get to safety. Fighting the fire from the air cannot be carried out either, because this is no longer possible with the winds that occur at speeds of 50 to 60 meters per second. In a normal forest fire, a firefighter is exposed to a heat output of 10,000 kilowatts per meter of fire front. The thermal output of a PyroCb is 60,000 to 90,000 kilowatts per meter. In New South Wales, firefighters are trained on the dangers posed by the PyroCb. The emergence of a PyroCb can be recognized when a cloud of fire rises more than five kilometers into the atmosphere and becomes white again through the formation of ice crystals.
See also
Individual evidence
- ↑ a b c Graham Readfearn: Scientists fear surge in supersized bushfires did create Their Own violent thunderstorms , January 4th 2020, The Guardian .
- ↑ a b Ralf Nestler: Fires in Siberia and Alaska are fueling climate change , August 9, 2019 on Tagesspiegel .
- ↑ Andrew Tupper, J. Scott Oswalt, Daniel Rosenfeld: Satellite and radar analysis of the volcanic ‐ cumulonimbi at Mount Pinatubo, Philippines, 1991 , May 11, 2015 on Journals of Geophysical Research
- ↑ a b c d e Fire that cannot be fought , December 22, 2019 on Spiegel Online .
- ↑ a b When bushfires make their own weather , from January 8, 2018 on BOM GOV.
- ↑ Michael Finneran: Fire-Breathing Storm Systems , on NASA Langley Research Center. Retrieved January 24, 2020
- ↑ a b Christopher Brito: Australia bushfires creating the "pyrocumulonibus" thunderstorms that can start new fires , December 30, 2019 on CBS News.
- ↑ When bushfires make their own weather January 8, 2018 on Bureau of Meteorology Australia.
- ↑ David Peterson, James Campbell, Edward Hyer et al: Wildfire-driven thunderstorms cause a volcano-like stratospheric injection of smoke
- ↑ a b Flight through a Fire Cloud , August 13 at NASA Earth Observatory.
- ↑ Michael Fromm, Daniel T. Lindsey, René Servranckx et al: The untold Story of Pyrocumulonimbus from March 31, 2010 on Journals Ametsoc. P. 1195.
- ↑ Andrew J. Dowdy, Michael D. Fromm, Nicholas McCarthy: Pyrocumulonimbus lightning and fire ignition on Black Saturday in southeast Australia July 17, 2017 on Journals of Geophysical Research.
- ↑ Michael Fromm, Daniel T. Lindsey, René Servranckx et al: The untold Story of Pyrocumulonimbus March 31, 2010 on Journals online. P. 1194.