The record increase of temperature caused by burned in British Columbia, Canada, is bringing another even more dangerous effect: “fire-breathing” clouds, or “pyrocumulonimbus”, if you prefer the technical term.
According to the authorities looking into the situation, these clouds could further complicate a problem that is already very difficult to control, since, as a result of them, new fires could arise and expand the problem of fires.
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The temperature in Lytton, just over 150 kilometers (km) from Vancouver, reached an incredible 49,5 degrees Celsius (°C) last Tuesday (29/6), thanks to a heat wave which generated a fire in the plains region of the village. The mayor ordered the evacuation of 250 residents. On Thursday (1), the burning, which already reached sizes of 20 thousand acres, had destroyed 90% of the region, with residents saying phrases like “our village disappeared” on social networks.
According to Dakota Smith, a collaborative meteorologist at the Colorado Atmospheric Research Institute, “feathers” indicative of the formation of a pyrocumulonimbus cloud were seen in images from satellite.
But what are the “pirocumulonimbus”, after all?
The clouds known as “pirocumulonimbus” are artificial clouds originated from fires in forest or plain regions. Basically, they're easier to understand if you think of them as “born” from fire, to bring in more fire. Including, its name in Latin - "cumulonimbus flammagenitus” – can be translated to “created by the flame”
Explaining in scientific terms: a common cumulonimbus brings with it electrical storms, being formed after warm moist air rises from the ground to the atmosphere. Once up there, that air cools and descends back to Earth, reheating and rising again. This “up-and-down” is what generates clouds that cause electrical storms.
Pirocumulonimbus go through the same process: however, moist, warm air comes from the flames and smoke of a fire, not the ground: if you see images of a forest fire, for example, and identify thick, dense clouds, they will always be pirocumulonimbus .
Although they can also generate electrical storms like their “sister”, a more common effect is a powerful “blast” of dry air that it blasts toward the ground. When this dry air touches the ground in the middle of a fire, the fire and smoke build up and spread, generating more hot air and moisture and new clouds like that, which will hurl new gusts to the ground – a very hot vicious cycle.
The village of Lytton was not the first to face the problem: in September 2020, fires in California, USA, were caused by one of the largest pyrocumulonimbus clouds recorded in the country's history, with almost 650 square kilometers (km²) of size.
Another well-remembered incident is the fire in Canberra, Australia, in 2003. In this example, another effect was also present: the air around a pirocumulonimbus began to rotate, creating a circular current – a kind of column which eventually turned into a “fire tornado”.
Global Warming Makes Problems Worse
The increase in temperature and dry air – two elements associated with forest fires and other natural occurrences – can be attributed to global warming, according to scientists. And as this volume is only increasing, fires of this type (and, consequently, the creation of pirocumulonimbus) are becoming more and more frequent.
In 2002, the three North American countries saw a combined 17 storms of this type. Almost 20 years later, this average jumped to 25 only in the western United States, not counting the other territories, according to an analysis published by Yale360, a page linked to Yale University.
Studies indicate that these storms are so intense that they penetrate the stratosphere – which starts about 50 km above the ground – and may remain there for years. Research conducted in 2018 revealed that a single large pyrocumulonimbus sends so many particles into the stratosphere that its effect is comparable to that of a medium-sized volcanic eruption.
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