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CSU\u2009\/\u2009CIRA & JAXA\u2009\/\u2009JMA <\/span><\/a> The Tonga eruptionCSU\u2009\/\u2009CIRA & JAXA\u2009\/\u2009JMA <\/span><\/p><\/div>\n The unusual cloud of suspended particles observed by the radar was a result of the major eruption of Hunga Tonga\u2013Hunga Ha’apai, an underwater volcano located 65 kilometers north of the main island of the Tonga archipelago in the South Pacific, on January 15. The volcanic activity was so intense that it split Hunga Tonga\u2013Hunga Ha\u02bbapai into two. Shortly after the event, scientists from countries in the Southern Hemisphere, such as Australia and New Zealand, began tracking the smoke plume using radar, satellites, and other instruments.<\/p>\n The major volcanic explosion in Tonga caused a tsunami, with waves up to 15 meters high reaching the islands of the archipelago, home to 100,000 people. At least six people died and thousands were left homeless. The noise of the eruption was heard in New Zealand, nearly 2,000 kilometers away. An enormous plume of volcanic ash covered Tonga for 11 hours. It was formed primarily of sulfur-based gases, water vapor, and carbon dioxide.<\/p>\n In mid-February, researchers from NASA conducted a preliminary analysis of data from two geostationary weather satellites, GOES-17 and Himawari-8, concluding that the volcanic plume from Hunga Tonga\u2013Hunga Ha\u02bbapai reached the highest altitude ever recorded for this type of phenomenon. Thirty minutes after the eruption, the cloud of gas, steam, and ash expelled by the submarine volcano in the South Pacific reached an altitude of 58 km, penetrating the mesosphere, the third layer of the atmosphere, which stretches from approximately 50 km to 100 km in altitude. “The intensity of this event far exceeds that of any storm cloud I have ever studied,” said Kristopher Bedka, a climate scientist from the NASA Langley Research Center, in a press release. The previous record was held by the 1991 eruption of Pinatubo, a volcano located in the Philippines, which ejected ash to an altitude of 35 km.<\/p>\n NASA Earth Observatory<\/span><\/a> Satellite images show progress of underwater eruption and the volcanic plume it releasedNASA Earth Observatory<\/span><\/p><\/div>\n Volcanic eruptions so powerful that their plume reaches the stratosphere can temporarily alter the global climate, reducing the planet’s average temperature for several months. Aerosols block some sunlight from reaching Earth, cooling the environment (see<\/em> Pesquisa FAPESP issue<\/em> no. 308<\/em>), hence the interest in these extreme events among atmospheric scientists, as well as geologists and volcanologists, of course. \u201cThe aerosols from the Pinatubo eruption cooled the planet\u2019s average temperature by about 0.6 \u00b0C for almost two years,\u201d says M\u00e1rcia Akemi Yamasoe, a physicist from the Institute of Astronomy, Geophysics, and Atmospheric Sciences (IAG) at the University of S\u00e3o Paulo (USP). “But it’s too early to predict whether the Tonga eruption will have a similar impact on the global climate.”<\/p>\n Unlike in the troposphere, which is the lowest layer of the atmosphere, there are no rain clouds in the stratosphere or mesosphere. This makes pollutant dispersal slower in the upper layers of the atmosphere, which has so far been the case for the Tonga volcanic plume. \u201cAerosols can circulate around the globe for months or even years,\u201d says Landulfo.<\/p>\n The IPEN weather radar uses lidar technology, a remote sensing method in which a laser measures the location of objects relative to the Earth’s surface. Because we know the speed of light (about 300,000 km per second), we can use the time a laser beam takes to bounce off a layer of aerosols and return to its source to calculate the exact distance to a cloud of suspended particles.<\/p>\n F\u00e1bio Juliano da Silva Lopes\u2009\/\u2009IPEN<\/span><\/a> IPEN weather radar shows the volcanic plume from the eruption of the Tonga volcano 27 km above S\u00e3o Paulo (green line at the top of the image<\/em>)F\u00e1bio Juliano da Silva Lopes\u2009\/\u2009IPEN<\/span><\/p><\/div>\n The IPEN radar is specifically programmed to detect the presence of aerosols ranging from a few nanometers to a few micrometers in diameter, such as urban pollution, smoke from fires, water vapor, and dust. It is primarily used to study air quality and climate in Greater S\u00e3o Paulo and is part of the Latin American Lidar Network (LALINET).<\/p>\n \u201cSince we first identified the plume from the Tonga volcano eruption, we have been using the radar to follow its movement whenever the observation conditions at night are good enough\u201d, says F\u00e1bio Juliano da Silva Lopes, a physicist doing a postdoctoral fellowship in Landulfo’s group at IPEN. On some days, researchers at the institute noted that the plume was actually divided into three clouds located at different altitudes of around 22, 25, and 27 km.<\/p>\n Preliminary data from international sources indicate that the Tonga submarine eruption likely reached level 5 on the Volcanic Explosivity Index (VEI), a logarithmic scale ranging from 0 (weakest) to 8 (strongest). The index provides a relative power rating of volcanic eruptions, similar to the better-known Richter scale, which measures the magnitude of earthquakes. The volcanic explosion that occurred earlier this year on the outskirts of the Tonga archipelago in the South Pacific was the most powerful since the 1991 Pinatubo eruption, which reached a VEI of six.<\/p>\n