The bushfires in Australia are now so big that they are generating their own weather, in the form of giant thunderstorms that start more fires, according to the Bureau of Meteorology in Victoria.
Bushfires Generate Their Own Weather
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Pyro-cumulonimbus clouds have developed to altitudes over 16km in East Gippsland this afternoon. These fire-induced storms can spread fires through lightning, lofting of embers and generation of severe wind outflows. Intense fires generate smoke, obviously. But their heat can also create a localised updraft powerful enough to create its own changes in the atmosphere above.
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As the heat and smoke rise, the cloud plume can cool off, generating a large, puffy cloud full of potential rain. The plume can also scatter embers and hot ash over a wider area. Eventually, water droplets in the cloud condense, generating a downburst of rain – maybe. But the ‘front’ between the calm air outside the fire zone and a pyro cumulonimbus storm cloud is so sharp that it also generates lightning and that can start new fires. If powerful enough, a pyro cumulonimbus storm can generate a fire tornado, which happened during the Canberra bushfires in 2003.
Why do Pyrocumulus clouds rise above the smoke?
This moisture then accumulates on smoke particles and rapidly condenses as it rises. Pyrocumulus clouds are more commonly seen above volcanic eruptions, which produce lots of steam. If you've ever seen an evil-looking cloud creating dry lightning above a volcano, that's a pyrocumulus cloud.
Scientists worry that ‘pyroCbs’ are on the rise around the world, driven by warmer temperatures and more intense fires. Their plumes are so strong that they can even shoot smoke into the stratosphere, 6 to 30 miles (10 to 50 kilometres) above the Earth's surface.
Bushfires Australia Generate Their Own Weather. Time lapse of a pyro cumulonimbus storm in action
What types of clouds are associated with wildfires?
Simply put, it is a cumulus cloud that is formed by hot air and smoke being released into the sky, usually during volcanic eruptions, or in Australia’s case, by wildfires. The clouds are usually gray, black or brown
Smoke From Bushfires In Australia Has Spread To South America
Smoke particles from bushfires in Australia have reached South America, in a striking illustration of the intensity of the unprecedented blazes.
Satellites show atmospheric pollution created by the fires across New South Wales and Queensland has travelled more than 10,000 kilometres to Chile and Argentina. Researchers at the European Centre for Medium-Range Weather Forecasts (ECMWF) in Reading, UK, found a plume of carbon monoxide and aerosols trailing across the Pacific Ocean to South America.
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More pollution will follow, judging from the situation in Australia. From satellite imagery there’s thick smoke coming out of New South Wales, so more will be being pumped out, meaning a train of pollution going across the south Pacific, will follow the jet stream.
What is jet stream in geography?
A jet stream is defined as a current of rapidly moving air that is usually several thousand miles long and wide but is relatively thin. They are found in the upper levels of Earth's atmosphere at the tropopause - the boundary between the troposphere and stratosphere (see atmospheric layers).
While it is relatively unusual for pollution to travel so far, studies have shown Australia’s deadly 2009 “Black Saturday” fires released materials that travelled a similar distance. Only trace amounts of Australian pollution hitting South America have been recorded today by satellites, with carbon monoxide levels of 80 to 100 parts per billion. Anything above 110ppb is considered polluted air.
Australia’s deadly 2009 'Black Saturday' fires
However, it is unlikely the pollution will affect local air quality in South America which has experienced its own serious forest fires this year since the material is around 5 kilometres up in the atmosphere and likely to stay there. If the air comes down and reaches the surface it could add an extra bit on top of local air quality issues.
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Instead, the significance of the pollution reaching so far is what it tells us about the power of the fires in Australia. It’s reflecting the sheer intensity of the fires, particularly in New South Wales.
Smoke From Bushfires In Australia Reach New Zealand
Across the Tasman Sea, smoke from the wildfires are posing a new threat to New Zealand’s white glaciers, turning them black and staining snow brown.
Social media posts from tourists and helicopter services from the Franz Josef and Tasman glaciers show 'caramelised' snow and smoke-shrouded views. A climber who posted a video from the top of the Tasman glacier added: “We can actually smell the burning here in Christchurch.”
Ash from the smoke could accelerate melting snow on the glaciers, which already face a climate disaster of their own. The whiteness of snow and ice reflects the sun’s heat and slows melting, but as ash and dust settle on the snow, it absorbs more heat and melts at a faster rate.
How does the albedo effect work?
The albedo effect. Light surfaces reflect more heat than dark surfaces. This is called the albedo effect. When the Earth's temperature dropped because of its position in orbit around the Sun, and the tilt of the axis, the ice sheets grew.
Over 3,000 glaciers in New Zealand are quickly disappearing due to global warming and many could completely melt away by the end of the century. If the ash stays on the surface then it will certainly enhance melt. If fire frequency, ash and dust transport increase, there is a chance that this will hasten the demise of New Zealand’s glaciers.
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