Pyrocumulus
Pyrocumulus ( fire cloud ) is a type of cloud that occurs as a result of fire storms . These are particularly high, sooty clouds that can bring massive storms and thunderstorms with them. When it comes to fire clouds, a distinction is made between pyrocumulus and pyrocumulonimbus . The main difference is that pyrocumulonimbi ascend into the lower stratosphere .
Pyrocumuli
Pyrocumuli can be caused by intense heating of the earth's surface Volcanic eruptions ( eruption thunderstorms ), forest fires or industrial fumes arise: The convection generated causes the air masses to rise to a stable point, which is usually accompanied by an increase in humidity . A weak jet stream can promote cloud formation. The atmospheric humidity, the evaporating amounts of water from forest and bush fires or volcanoes condense on the ash particles rising up. Pyrocumulus clouds often lead to violent turbulence , which can trigger or intensify a conflagration on the ground due to strong gusts . Ashes and smoke make pyrocumuli often look gray or brown. From a certain size of the cloud, moisture is also sucked up with the rising air, so that from a point onwards enough precipitation falls that the fire that caused the pyrocumulus may be extinguished.
Pyrocumulus and Pyrocumulonimbus
Smoke develops over ground fires because the moisture it contains condenses in plants and the humidity in the atmosphere. The cloud that forms is commonly referred to as a cloud of fire, or pyrocumulus. There is also another cloud of fire, the pyrocumulonimbus, which is much larger. This type of fire cloud has been known for a long time, but not all aspects have been researched.
If the ground fire gets bigger, another type of fire cloud can develop, the pyrocumulonimbus (PyroCb). This cloud of fire is capable of generating lightning, thunderstorms and storms. This PyroCb creates its own weather. It accelerates the fires on the ground, makes them hotter, creates new ground fires through lightning and carries smoke aerosols into the lower stratosphere, which can spread worldwide. The formation of a PyroCb is visually recognizable when a cloud of smoke rises over five kilometers and turns white above it (see illustration). If a PyroCb has arisen, it can no longer be fought on the ground because of the great heat and fire extinguishing from the air is no longer possible because of the squalls.
It used to be assumed that only volcanic eruptions are able to transport aerosols into the lower stratosphere . The PyroCb can transport smoke aerosols in the amount of a medium volcanic eruption into the lower stratosphere and spread them worldwide. Meanwhile one also assumes that in nuclear explosions resulting so-called mushroom cloud a PyroCb is because this cloud can not rise due to the nuclear explosion, but due to the arising after the explosion heat to the lower stratosphere.
literature
- Gavin Pretor-Pinney: The Cloud Collector's Handbook . Chronicle Books, San Francisco 2011.
Web links
Individual evidence
- ↑ Christoph Seidler: Fire that cannot be fought , December 22, 2019 on Spiegel-online .
- ↑ Bushfires in Australia generate their own weather , January 8, 2020 on Spiegel Online.
- ↑ When bushfires make their own weather , Jan. 8, 2018 on Government of Australia.
- ↑ David Peterson, James Campbell, Edward Hyer et al: Wildfire-driven thunderstorms cause a volcano-like stratospheric injection of smoke , August 20, 2018 on Nature
- ↑ Flight through a Fire Cloud , August 13, 2019 on NASA Earth Observatory
- ↑ William J. Broad: The Hiroshima Mushroom Cloud That Wasn't , May 23, 2016 in the New York Times
- ↑ Frances Mao: Australia fires: How extreme 'firestorms' make their own weather November 13, 2019 on BBC News