Elusive atmospheric wave detected during Tonga volcanic eruption

Satellite image of the Tonga volcanic eruption, 2022. (Photo credit: NASA Worldview, NOAA/NESDIS/STAR)

The catastrophic eruption of Hunga Tonga-Hunga Haʻapai volcano in 2022 triggered a special atmospheric wave that has escaped detection for the past 85 years. Researchers from the University of Hawaii in ManoaJapan Agency for Marine and Earth Science and Technology (JAMSTEC), and Kyoto University relied on state-of-the-art observational data and computer simulations to discover the existence of Pekeris waves – fluctuations in atmospheric pressure which were theorized in 1937 but whose existence in nature has never been proven until now.

The study was published in the Journal of Atmospheric Sciences.

The eruption in the South Pacific earlier this year triggered what was probably the most powerful explosion the world has seen since the famous 1883 eruption of Mount Krakatau in Indonesia. The rapid release of energy excited pressure waves in the atmosphere that quickly spread around the world.

The atmospheric wave pattern near the eruption was quite complicated, but thousands of miles away the disturbances were caused by an isolated wavefront moving horizontally at over 650 miles per hour as it spread outward. The atmospheric pressure disturbances associated with the initial wavefront have been clearly observed on thousands of barometric records around the world.

“The same behavior was observed after the eruption of Krakatau, and in the early 20th century a physical theory of this wave was developed by the English scientist Horace Lamb,” said Kevin HamiltonProfessor Emeritus of Atmospheric Sciences at uh Manoa School of Ocean and Earth Science and Technology. “These movements are now known as Lamb waves. In 1937, the American-Israeli mathematician and geophysicist Chaim Pekeris extended Lamb’s theoretical treatment and concluded that a second-wave solution with a slower horizontal velocity should also be possible. Pekeris tried to find evidence of his slower wave in pressure observations after the Krakatau eruption but failed to produce a convincing case.

Succeed in identifying the wave

Scientists applied a wide range of tools now available, including geostationary satellite observations, computer simulations and extremely dense networks of atmospheric pressure observations to successfully identify the Pekeris wave in the atmosphere after the Tonga eruption.

Lead author Shingo Watanabe, deputy director of the Japan Agency for Marine and Earth Science and Technology‘s Environmental Modeling Research Center, performed computer simulations of the Tonga eruption response.

“When we studied the simulated and computer-observed pulses over the entire Pacific basin, we found that the slower wavefront could be observed over large regions and that its properties matched those predicted by Pekeris he nearly a century ago,” Hamilton said.

Watch an animation of the global atmosphere after the Tonga eruption.

For more information, see SOESTthe website of.

About Shirley L. Kreger

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