Atmospheric super-rotation is a phenomenon where a planet's atmosphere rotates faster than the planet itself. This behavior is observed in the atmosphere of Venus, atmosphere of Titan, atmosphere of Jupiter, and atmosphere of Saturn. Venus exhibits the most extreme super-rotation, with its atmosphere circling the planet in four Earth days, much faster than its planet's own rotation. The phenomenon of atmospheric super-rotation can influence a planet's climate and atmospheric dynamics.
In understanding super-rotation, the role of atmospheric waves and instabilities is crucial. These dynamics, including Rossby waves and Kelvin waves, are integral in transferring momentum and energy within atmospheres, contributing to the maintenance of super-rotation. For instance, on Venus, the interaction of thermal tides with planetary-scale Rossby waves is thought to contribute significantly to its rapid super-rotational winds. Similarly, in Earth's atmosphere, Kelvin waves generate eastward along the equator, playing a vital role in phenomena like the El Niño-Southern Oscillation, demonstrating the broader implications of these dynamics in atmospheric science.[1][2]
The atmosphere of Venus is a prominent case of extreme super-rotation; the Venusian atmosphere circles the planet in just four Earth days, much faster than Venus' sidereal day of 243 Earth days.[1] Atmospheric super-rotation has also been observed on Titan, Saturn's largest moon, exhibiting large stratospheric zonal winds reaching a super-rotation ten times greater than its sidereal day of 16 Earth Days. The initial observations of Venus and Titan's super rotation were based on Earth-based observation, however, future measurements confirmed this through the use of the Huygens probe.[2]
The visible cloud tops of Jupiter and Saturn provides further evidence on its deep atmospheric circulation demonstrating the presence of atmospheric super-rotation.[3] Jupiter's auroras, in particular, highlight the planet's rapid atmospheric movements through their ethereal glow and varying cloud depths.
On Earth, there is a phenomenon that its thermosphere has a slight net super-rotation, exceeding the surface rotational velocity. The size of this phenomenon varies widely across different models.[4][5][6] Some models suggest that global warming is likely to cause an increase in super-rotation in the future, including possible change in surface winds patterns.[7][8]
Super-rotation in planetary atmospheres extends to the study of exoplanets, particularly, hot Jupiters. These distant worlds, orbiting close to their stars, often exhibit extreme atmospheric conditions, including super-rotation, which influences their thermal structures and potential habitability. Observations from telescopes like the Hubble Space Telescope have unveiled super-rotational wind speeds of thousands of kilometers per hour on some hot Jupiters. Moreover, the phenomenon shows how hot Jupiters is tidally locked, where one side continuously faces the star. This suggests a mechanism for heat distribution in planets, a factor in understanding their climatic conditions and patterns.[3][4]