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Earth’s atmosphere “rings” like a bell

At the beginning of the 19th century, the physicist Pierre-Simon Laplace hypothesized that the atmosphere is traversed by pressure waves at the origin of a global phenomenon of atmospheric resonance. For many years, geophysicists will deepen and clarify this idea, in particular by identifying the frequencies expected for these waves. However, it was only recently that a team of researchers was finally able to identify and confirm the presence of these waves, causing the atmosphere to vibrate like a bell. 

A ringing bell vibrates simultaneously with a deep fundamental tone and numerous high harmonics, producing a characteristic musical sound. A recent study, published in the Journal of the Atmospheric Sciences by geophysicists at the University of Kyoto and the University of Hawaii at Mānoa, shows that the entire atmosphere of the Earth vibrates in an analogous manner, confirming theories developed by physicists over the past two centuries.

In the case of the atmosphere, “music” emerges in the form of large-scale atmospheric pressure waves covering the globe and travelling around the equator, some moving east to west and others moving west to east. Each of these waves is a resonant vibration of the global atmosphere.

The basic understanding of these atmospheric resonances began with ideas expressed at the beginning of the 19th century by one of the greatest scientists in history, the French physicist and mathematician Pierre-Simon Laplace. Research by physicists over the next two centuries refined the theory and led to detailed predictions of the frequencies of the waves that should be present in the atmosphere. However, the actual detection of such waves lagged behind the theory.

Pressure waves at the origin of a real atmospheric resonance

The new study by Takatoshi Sakazaki, professor at the Graduate School of Science at Kyoto University, and Kevin Hamilton, professor at the Department of Atmospheric Sciences and at the International Pacific Research Center at the University of Hawaii, presents a detailed analysis of the atmospheric pressure observed on the globe every hour for 38 years. The results clearly revealed the presence of dozens of previously predicted wave modes.

The study focused in particular on the waves with periods between 2 hours and 33 hours which move horizontally through the atmosphere, moving around the globe at high speed (exceeding 310 km / h). This establishes a characteristic “checkerboard” pattern of high and low pressure, associated with these waves as they propagate.

“ Our identification of so many modes in real data shows that the atmosphere sounds good as a bell. This finally solves an old and classic problem in atmospheric science, but it also opens up a new avenue of research to understand both the processes that excite waves and the processes that act to dampen waves, “Hamilton concludes.

Sources:  JAS

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