Venus’ atmosphere jumps and waves

The mysterious origin of an impressive cloud disturbance on Venus has now been revealed by a team including the University of Tokyo. Researchers used numerical models to show that an enormous 6,000-kilometer-wide atmospheric wave front, which circumnavigates the planet for days at a time, is caused by a large “hydraulic jump.” This is when a fluid abruptly slows down, changing from shallow and fast to deep and slow. On Venus, a sudden change in airflow in the lower cloud region is coupled with the creation of a strong updraft, forcing sulfuric acid vapor higher into the atmosphere where it condenses into a massive line of cloud. Future planetary studies can consider the potential impacts of this process, and what it might mean for any exploratory missions.   

A grim, gray day may spoil weekend plans now and then, but on Venus, it’s cloudy all day every day with a chance of sulfuric acid showers. On the bright side, Venus’ constant thick cloud cover provides an excellent opportunity for us to study patterns and processes that would be difficult to spot on planets where clouds are more sparse or intermittent, like here on Earth.

A key feature of Venusian clouds is that they “superrotate,” moving about 60 times faster than the planet turns. We now know that superrotation also occurs elsewhere, including on Mars, our sun, and even Earth’s upper atmosphere. In 2016, images from Japan’s Akatsuki Venus orbiter also revealed that an enormous atmospheric wave — sometimes 6,000 km wide — repeatedly sweeps around the planet’s equator.

“We identified the phenomena, but for years we couldn’t understand it,” said Professor Takeshi Imamura from the Graduate School of Frontier Sciences at the University of Tokyo. “However, thanks to this research, we’re now able to show that this cloud disruption is caused by the largest known hydraulic jump in the solar system.”

We can see a hydraulic jump in action in the humble kitchen sink. As water from the tap hits the basin, it appears fast and shallow at first, but suddenly slows and becomes deeper as it spreads.

The hydraulic jump on Venus occurs when an eastward-moving atmospheric wave (called a Kelvin wave) in the lower to middle cloud region suddenly becomes unstable. Wind speed as seen from the atmospheric wave abruptly slows down and a strong localized updraft is created, which carries sulfuric acid vapor higher into the atmosphere. The droplets condense into clouds which trail behind, causing the massive wave front which can be seen sweeping around the planet.

“Venus has three distinct cloud layers, and the dynamics of the lower and middle layers are not so well understood,” said Imamura. “Our discovery of a hydraulic jump on Venus connecting a very large-scale horizontal process with a strong localized vertical wave is unexpected, as in fluid dynamics these are usually disconnected.”

The hydraulic jump was simulated using a fluid dynamic model (a numerical analysis which simulates how gas or liquids flow), and the cloud formation studied using a microphysical box model (which follows the behavior of an example section of air as it moves through the atmosphere). As well as simulating the same cloud disturbance, the team also found that this process helps to maintain the superrotation of Venus’ atmosphere.

“Up until now, we used a global circulation model (GCM) for Venus that is similar to Earth’s, but this model doesn’t include the hydraulic jump which we have now identified,” explained Imamura. “Our next step will be to test this discovery within a more inclusive climate model that includes other atmospheric processes. We will face some challenges due to the huge amount of processing power required to run such simulations. Even with modern supercomputers, it isn’t easy.”

Although this is the first observation of a hydraulic jump of this scale on another planet, the physics behind it may also occur on other celestial bodies. “Under some circumstances, Mars’ atmosphere may also have the right conditions for a hydraulic jump,” mentioned Imamura. Creating more accurate models of atmospheric conditions will aid in the success of future missions to Mars, as well as wider space exploration.  

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Journal:

Takeshi Imamura, Yasumitsu Maejima, Ko-ichiro Sugiyama, Takehiko Satoh, Javier Peralta, Kevin McGouldrick, Takeshi Horinouchi, Kohei Ikeda, “A planetary-scale hydraulic jump driving Venus' cloud front”. Journal of Geophysical Research: Planets. April 24 2026. DOI: 10.1029/2026JE009672

Funding:

This work was funded by JSPS KAKENHI Grant Numbers 24H00021, 24K21565, and 23H01236. J.P. acknowledges project EMERGIA20_00414 funded by Junta de Andalucía in Spain, and project PID2023-149055NB-C33 funded by the Spanish MCIN.

Conflicts of Interest:

The authors declare there are no conflicts of interest for this manuscript.

Useful links:

Graduate School of Frontier Sciences: https://www.k.u-tokyo.ac.jp/en/

JAXA's Akatsuki website: https://akatsuki.isas.jaxa.jp/en/

Research Contact:

Professor Takeshi Imamura

Department of Complexity Science and Engineering
Graduate School of Frontier Sciences

The University of Tokyo

5-1-5 Kashiwanoha

Kashiwa, Chiba 277-0882

JAPAN

t_imamura@edu.k.u-tokyo.ac.jp

Press contact:

Mrs. Nicola Burghall

Strategic Communications Group,

The University of Tokyo,

7-3-1 Hongo, Bunkyo-ku,

Tokyo, 113-8656, Japan

press-releases.adm@gs.mail.u-tokyo.ac.jp

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