Dec. 19 (UPI) -- Scientists can finally explain why Jupiter's jet stream regularly reverses course -- like clockwork. The revelation could help scientists better understand similar equatorial jet stream oscillations found on Earth and Saturn.
The latest research -- published this week in the Journal of Geophysical Research-Planets -- reveals that gravity waves are the primary driver of the reversal of Jupiter's equatorial jet stream.
Researchers first discovered Earth's equatorial jet stream after watching ash from the 1883 eruption of the Krakatoa volcano being blown from east-to-west. Hot air balloons later confirmed the stratospheric current.
The jet stream begins in the lower stratosphere and moves toward the upper troposphere, the lowest level of Earth's atmosphere. The current regularly reverses course, with each phase lasting roughly 28 months. The phenomenon is called the quasi-biennial oscillation, or QBO.
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Jupiter's phenomenon is called the quasi-quadrennial oscillation, or QQO, with each phase lasting four Earth years. Scientists were able to study the pattern in greater detail than ever before using instruments at NASA's Infrared Telescope Facility.
Scientists imaged the jet stream across a larger area and longer timespan, but at much higher resolutions than previous efforts.
"These measurements were able to probe thin vertical slices of Jupiter's atmosphere," Amy Simon, a planetary scientist at NASA's Goddard Space Flight Center in Maryland, said in a news release. "Previous data sets had lower resolution, so the signals were essentially smeared out over a large section of the atmosphere."
The precision detail and broad perspective allowed scientists to identify the driver of the wind pattern. Scientists built an atmospheric model using data collected during the comprehensive survey of Jupiter's QQO. Simulations suggest gravity waves produced in the lower atmosphere are propagated upward where they cause the equatorial jet stream to reverse course.
Scientists hypothesize that gravity waves are also a major driver of Earth's QBO reversal, but aren't powerful enough to power the oscillation alone.
"Despite the many differences between Earth and Jupiter, the coupling mechanisms between the lower and upper atmospheres in both planets are similar and have similar effects," said Raúl Morales-Juberías, an associate professor at the New Mexico Institute of Mining and Technology in Socorro. "Our model could be applied to study the effects of these mechanisms in other planets of the solar system and in exoplanets."
