This image taken by a Japanese weather satellite shows the eruption plume of the Hunga Tonga-Hunga… [+] Ha’apai Volcano on Saturday, January 15, 2022.
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Using satellite images, researchers from the University of Oxford’s Department of Physics and the Rutherford Appleton Laboratory have confirmed that the January 2022 eruption of the Hunga Tonga-Hunga Ha’apai volcano produced the highest plume never registered The colossal eruption is also the first directly observed to have ruptured the mesosphere layer of the atmosphere, about 50 kilometers above the Earth’s surface.
On January 15, 2022, Hunga Tonga–Hunga Haʻapai, an underwater volcano in the Tonga archipelago in the South Pacific Ocean, violently erupted. The blast was one of the most powerful ever seen, sending shockwaves around the world and triggering devastating tsunamis that left thousands homeless. A plume of ash and water was ejected into the atmosphere, but until now, scientists had no precise way to measure its height.
Typically, the height of a volcanic plume can be estimated by measuring the temperature recorded at the top by infrared-based satellites and comparing it to a reference vertical temperature profile. This is because in the troposphere (the first and lowest layer of the Earth’s atmosphere), the temperature decreases with height. But if the eruption is so large that the plume penetrates the next layer of the atmosphere (the stratosphere), this method becomes ambiguous because the temperature begins to rise again with height (due to the layer of ‘ozone that absorbs solar ultraviolet radiation).
To overcome this problem, the researchers used a new method based on a phenomenon called the “parallax effect”. This is the apparent difference in the position of an object when viewed from multiple lines of sight. You can see this for yourself by closing your right eye and holding out a hand with a thumbs up. If you switch eyes so that your left is closed and your right is open, your thumb will appear to move slightly against the background. By measuring this apparent change in position and combining it with the known distance between the eyes, you can calculate the distance to the thumb.
The location of the Tonga volcano is covered by three geostationary weather satellites, so the researchers were able to apply the parallax effect to the aerial images they captured. Crucially, during the eruption itself, the satellites recorded images every 10 minutes, allowing the rapid changes in the plume’s trajectory to be documented.
The full disk of the Earth as seen by the Japanese Himawari-8 satellite, the volcanic eruption is at the bottom… [+] right
Simon Proud / Uni Oxford, RALSpace NCEO / Japan Meteorological Agency
The results showed that the plume reached an altitude of 57 kilometers at its maximum extent. This is significantly higher than the previous records: the 1991 eruption of Mount Pinatubo in the Philippines (40 km at its highest point) and the 1982 eruption of El Chichón in Mexico (31 km). It also makes the plume the first observational evidence of a volcanic eruption injecting material through the stratosphere and directly into the mesosphere.
Lead author Dr Simon Proud explains: “This is an extraordinary result as we have never seen a cloud of any kind this high before. Also, the ability to estimate the height in the way we did to do is only possible now that we have good satellite coverage. It wouldn’t have been possible a decade or so ago.”
Oxford researchers intend to build an automated system to calculate volcano plume heights using the parallax method. The co-author, Dr. Andrew Prata, added: “We would also like to apply this technique to other eruptions and develop a dataset of plume heights that volcanologists and atmospheric scientists can use to model the dispersion of volcanic ash in the atmosphere. A more The science questions we’d like to understand are: Why did the Tonga plume get so high? What will be the climate impacts of this eruption? And what exactly was the plume made of?”
The article “The January 2022 eruption of the Hunga Tonga-Hunga Ha’apai volcano reached the mesosphere” is published in Science (2022). Material provided by the University of Oxford.