With the powerful cloud of smoke from the devastating wildfires in eastern Australia, ash and soot particles reached the stratosphere.
Build: AP
Large wildfires not only have dramatic effects on the ground, but also in the upper layers of the atmosphere. Rising aerosols destroy the protective ozone layer there.
Cumulonimbs are certainly the most impressive and dangerous clouds in our weather patterns. These massive storm clouds extend from a few hundred meters above the ground to the edge of the stratosphere, which begins at around 15 kilometers. Their umbrella, the so-called anvil, can reach a diameter of more than 150 kilometers. It is extremely turbulent within these clouds. They generate lightning, and they can produce heavy rain, tennis ball-sized hailstones, and snow as precipitation. However, cumulonimbus clouds are not only formed when moist air masses warm up more and more and rise rapidly to great heights. They can also form over the increasingly common large-scale wildfires and forest fires. These clouds, known as pyrocumulonimbes, transport large quantities of smoke particles and organic molecules into the stratosphere. Measurements by a Canadian research satellite have now shown that these substances cause chemical chaos there and even attack the ozone layer.
Pyrocumulonimbus clouds have been observed in major fires caused by heavy bombing during World War II. After the Hamburg firestorm of July 25, 1943, there were reports of clouds of smoke reaching the edge of the stratosphere. The US Air Force even photographed a pyrocumulonimbus over the devastating conflagration created by the atomic bomb detonation over Hiroshima in August 1945. These clouds are feared above all because they vehemently fuel the fires. For example, the thermal buoyancy of the air above the fire is so strong that chimneys are formed in the atmosphere above the source of the fire, through which hot air races upwards at great speed. This in turn creates such a strong negative pressure on the earth’s surface that fresh air from the environment flows at hurricane force in the direction of the seat of the fire and supplies the fires with more oxygen. In addition, the lightning generated in the pyrocumulonimbes can cause further forest fires if they strike combustible wood.