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Published November 10, 1994 | Published
Journal Article Open

Excitation of atmospheric oscillations by volcanic eruptions


We investigated the mechanism of atmospheric oscillations with periods of about 300 s which were observed for the 1991 Pinatubo and the 1982 El Chichón eruptions. Two distinct spectral peaks, at T = 270 and 230 s for the Pinatubo eruption and at T = 195 and 266 s for the El Chichón eruptions, have been reported. We found similar oscillations for the 1980 Mount St. Helens and the 1883 Krakatoa eruptions. To explain these observations, we investigated excitation problems for two types of idealized sources, "mass injection" and "energy injection" sources, placed in an isothermal atmosphere. In general, two modes of oscillations, "acoustic" and "gravity" modes, can be excited. For realistic atmospheric parameters, the acoustic and gravity modes have a period of 275 and 304 s, respectively. For a realistic time history of eruption, atmospheric oscillations with an amplitude of 50 to 100 Pa (0.5 to 1 mbar) can be excited by an energy injection source with a total energy of 10^17 J. This result is consistent with the observations and provides a physical basis for interpretation of atmospheric oscillations excited by volcanic eruptions.

Additional Information

© 1994 American Geophysical Union. Manuscript Accepted: 8 August 1994; Manuscript Received: 8 October 1993. Acknowledgments. We thank Andy Ingersoll for helpful discussions which motivated us to conduct this study. Discussions with Don Anderson and Tom Heaton helped us improve our understanding of the eruption process. We thank Raymond Hide for enlightening discussion on the physics of atmospheric waves. Reviews by Toshiro Tanimoto and Rudolph Widmer contributed to improvement of the manuscript. We thank George Stephens and Mike Matson, who provided us with the satellite image shown in Figure 11. This research was partially supported by the National Science Foundation grant EAR-92 18809. This is contribution 5320, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125.

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August 22, 2023
August 22, 2023