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The Earth's atmosphere vibrates like a giant bell: waves travel along the equator in both directions, encircling the globe. This conclusion was reached by scientists from Japan and the United States, confirming the long-standing hypothesis of atmospheric resonance. What is this phenomenon and can it be used to predict weather and long-term climate change?
In the early 19th century, the French physicist and mathematician Pierre-Simon Laplace compared the Earth's atmosphere to a vast ocean covering the planet and derived formulas known today as Laplace's tidal equations, which are used in calculations to make weather forecasts.
Laplace believed that the atmosphere has its own ebb and flow, as well as waves of air masses and thermal energy. Among other things, he mentioned vertical oscillations at the Earth's surface, propagating in the horizontal direction, which can be recorded by changes in surface pressure.
Atmospheric heat tides associated with the Earth's rotation have long been discovered by geophysicists. However, horizontal waves could not be detected. And now it's clear why.
As Takatoshi Sakazaki of the Graduate School of Science of Kyoto University and Kevin Hamilton, professor of the International Pacific Research Center at the University of Hawaii at Manoa, found out, Laplace waves have very large scales - they cover almost entire hemispheres - and very short periods, less than a day.
Therefore, they were overlooked in the study of local atmospheric phenomena, such as thunderstorms, and in the study of large, but long-term movements of air masses.
Diagram of horizontal wavelengths and periods of atmospheric phenomena that were previously studied by scientists. The star is tidal waves. Red contour - Laplace wave resonance zone
"Chessboard" of the Earth
The authors of the study analyzed data from the European Center for Medium-Range Weather Forecasts (ECMWF) for 38 years - from 1979 to 2016 inclusive, including hourly changes in surface atmospheric pressure across the entire surface of the planet. As a result, dozens of previously unknown wave modes were identified - systems of harmonic oscillations, which scientists call modes.
The researchers were especially interested in waves with short periods from two to 33 hours, propagating horizontally in the atmosphere around the globe at a tremendous speed - more than 1100 kilometers per hour.
The high and low pressure zones associated with these waves create a characteristic checkerboard pattern on the map, which, however, differs for each of the four main modes - Kelvin, Rossby, gravitational waves and a combination of the latter two.
A checkerboard pattern created by the low (blue) and high (red) pressure regions. As an example, two of the four main modes are shown - Kelvin and gravitational with periods of oscillation of the Earth's atmosphere 32, 4 and 9, 4 hours. Computer simulation results
It turned out that the Earth's atmosphere is like a ringing bell, when high overtones are superimposed on the main low-frequency background. It is this combination of deep background sound with subtle overflows that makes bell ringing so enjoyable.
Only the "music" of the Earth is not sound, but waves of atmospheric pressure, covering the entire globe. Each of the four main modes is a resonance of the atmosphere, by analogy with the resonances of a bell. In this case, low-frequency Kelvin waves propagate from east to west, and the rest - from west to east.
The scientists calculated the parameters of the resonance arising from the addition of all four modes, exactly coincided with the predictions of Laplace. And this confirmed his main idea that the weather is controlled by atmospheric pressure waves.
"It is gratifying that the vision of Laplace and other pioneer physicists has been fully confirmed two centuries later," Takatoshi Sakazaki quoted in a press release from the University of Hawaii at Manoa.
"Our identification of so many modes in real-world data shows that the atmosphere really rings like a bell," Hamilton continues.
The authors name the occurrence of hidden heating zones due to atmospheric convection and the cascade mechanism of propagation of turbulent energy flows as possible causes of global resonance.
Displacement of the regions of low (blue) and high (red) pressure for each of the four main modes: A - Rossby waves; B - Kelvin waves; С - gravitational waves; D - mixed mode Rossby - gravity
Equatorial winds in Antarctica
Another phenomenon associated with waves in the atmosphere was recently explained by American scientists from Clemson University in South Carolina and the University of Colorado at Boulder.
Observing polar vortices at McMurdo station in Antarctica - massive circular currents of cold air that spiral over each of the Earth's poles - they noticed that the Antarctic vortex is synchronous with the phases of quasi-biennial oscillations in the atmosphere (QBO).
Approximately every two years, latitudinal winds blowing at the Earth's equator change direction from east to west. The front begins at an altitude of more than 30 kilometers in the stratosphere and moves downward at a speed of about one kilometer per month. After 13-14 months, wind inversion occurs simultaneously along the entire equator. A complete cycle, therefore, takes from 26 to 28 months.
General scheme of quasi-biennial oscillations
The Americans found that during the eastern phase of the QBO, the Antarctic vortex expands and contracts during the western phase. This is explained by the passage of meridional gravitational waves from the equator to the poles through different layers of the atmosphere.
These waves were recorded and suggested that they are associated with a change in the direction of the winds blowing at the equator - at a distance of more than nine thousand kilometers from the observation site. Comparison with data from NASA's MERRA-2 meteorological and atmospheric observation system for the period from 1999 to 2019 fully confirmed this.
It has long been known that the expansion of the polar vortex zone brings cold weather to mid-latitudes. However, the fact that the root cause is a change in the direction of stratospheric winds in the tropics came as a surprise.
Scientists hope that the patterns they have identified will lead to more accurate climate and atmospheric circulation models for weather forecasting. At the same time, they are concerned that in recent decades, the impact of anthropogenic factors has been increasing.
So, four years ago, we noticed a violation of the cyclicity of the FTC. In February 2016, the transition to easterly winds was abruptly interrupted. One of the possible reasons is global warming.
Of even greater concern are the increasing frequency of extreme weather events, often also associated with atmospheric wave anomalies. In particular, scientists point to the occurrence of quasi-stationary atmospheric Rossby waves in the Northern Hemisphere.
Rossby Waves are giant bends in high-altitude winds that have a profound effect on the weather. If they pass into a quasi-stationary state, the change of cyclones and anticyclones is suspended. As a result, in some places it rains for weeks, turning into floods, while in others, an abnormal heat is set, as this year in the Arctic.
Heat waves and droughts hitting Central and North America, Central and Eastern Europe, the Caspian Sea region and East Asia several times over the summer and lasting one to two weeks, cause serious damage to agriculture. For several years in a row, harvests have been declining here, which complicates the social situation.
So the "music" of the Earth more and more often sounds not like a gentle melody, but an alarming alarm bell.