Just as the moon draws the water of the seas in our planet, which contributes to the occurrence of ocean waves and tides, it (with the sun) also pulls our atmosphere, which creates waves in the sky.
A new study, published in the Journal of Atmospheric Sciences on June 30, shows that some of these types of “sky waves” resonate around Earth, just as the sound waves echo bells.
Water waves and air waves
In water, waves are usually produced by passing energy. The energy that moves in our sky - from things like pressure from heat to gravitational pull of celestial bodies - also creates waves in the atmosphere.
But these atmospheric waves do not flow in the same way as ocean waves, but they can still be recognized if one realizes what they have to look for: moving pockets of tightly filled air thousands of kilometers away.
Previous studies of the phenomenon had focused on local spaces and limited time scales, which allowed them to discover sky waves whose width ranges between 1000 and 10,000 km, with a wave frequency for several hours, but the data available recently has now opened up to a much broader global view.
The ERA5 data set issued by the European Center for Medium-Range Weather Forecasts (ECMWF) provides hourly estimates of many atmospheric, terrestrial and ocean climate variables within 5 days of the actual time.
It also contains quantities of historical analyzes of these measurements, and this data set dates back to 1979.
This allowed Takatoshi Sakazaki of Kyoto University and atmospheric scientist Kevin Hamilton of University of Hawaii to explore atmospheric pressure data for 38 years.
That data included sky waves with frequencies between two hours and two days, and wavelengths greater than 5 thousand kilometers.
On this scale, the researchers were able to observe the previously discovered lunar and solar atmosphere waves together with "world-wide resonance patterns" that were first predicted in the 19th century by the famous French physicist Pierre Simon Laplace.
If the waves travel through the air at the appropriate height and speed, they may harmonize with the atmosphere, creating an echo, and this allows them to form a pattern stable enough to vibrate across the entire global atmosphere, such as sound waves that ring like a bell.
Indeed, researchers found groups of resonant sky resonant modes that spanned the world, and contributed to building atmospheric tonal layers similar to bell resonances, and this includes multiple resonance formats circling the equatorial regions.
"Our identification of several formats in the real data shows that the atmosphere actually has a resonance like a bell ring," Hamilton said.
The team also discovered a slight difference between the observed and expected frequencies of these resonant waves, which they concluded were due to the convergence of the waves from each other in the direction of their travel, thus increasing their frequency.
"With respect to these fast-moving wave patterns, our global frequencies and patterns match those expected in theory very well," said Sakazaki.
"It is exciting to see the ideas of Laplace and other pioneering physicists that have been fully validated after two centuries," he says.
Confirmation of these theories about atmospheric circulation and subsequent subtle tuning will allow scientists to develop more powerful models for weather and weather prediction.