Venus’ atmosphere jumps and waves

Making waves.These images taken on Aug. 18 (left) and Aug. 27 (right), 2016, by the near-infrared camera on Japan’s Akatsuki Venus probe, show the clear line of denser (darker) clouds moving across the planet.
Image Credit: ©T. Imamura, Y. Maejima, K. Sugiyama et al., 2026
(CC BY 4.0)

Scientific Frontline: Extended "At a Glance" Summary: Venusian Atmospheric Hydraulic Jumps

The Core Concept: A Venusian atmospheric hydraulic jump is an abrupt slowing and deepening of a fast-moving atmospheric fluid, which creates a massive 6,000-kilometer-wide wave front in the planet's cloud layer. It forces sulfuric acid vapor upward, condensing it into a distinctly visible, planetary-scale line of cloud.

Key Distinction/Mechanism: While typical atmospheric models treat large-scale horizontal processes and localized vertical waves as disconnected, this Venusian phenomenon uniquely links an unstable eastward-moving Kelvin wave with a severe vertical updraft. As wind speed abruptly drops, it creates the largest known hydraulic jump in the solar system, mechanically similar to the sudden transition from fast, shallow water to slow, deep ripples in a basin.

Major Frameworks/Components:

• Fluid Dynamic Models: Numerical analyses used to simulate the gas and liquid flow dynamics of the planetary-scale jump.
• Microphysical Box Models: Simulations tracking the behavior and condensation of sulfuric acid vapor as it moves vertically through the atmosphere.
• Kelvin Waves: Large-scale, eastward-moving atmospheric waves in the lower and middle cloud layers that become unstable and trigger the hydraulic jump.
• Superrotation Maintenance: The underlying mechanism by which the Venusian atmosphere rotates approximately 60 times faster than the planet itself, a process bolstered by these atmospheric disturbances.

Branch of Science: Planetary Science, Atmospheric Fluid Dynamics, Meteorology

Future Application: Integrating these hydraulic jumps into broad Global Circulation Models (GCMs) requires significant supercomputing power but will drastically improve the precision of planetary climate modeling. These refined models will aid in safely planning atmospheric entry and exploratory operations for future space missions to Venus, Mars, and other celestial bodies.

Why It Matters: Uncovering the mechanism behind this massive atmospheric wave solves a decade-long planetary mystery and reveals unexpected connections between horizontal and vertical fluid dynamics. Understanding these extreme weather patterns provides crucial insight into superrotation and the complex atmospheric behaviors of terrestrial planets.

Hydraulic jump simulation. This cross section of the Venusian atmosphere shows a numerical simulation of a hydraulic jump in action. The color indicates the “potential temperature,” which represents the atmospheric material surface. The jump appears as a stepwise transition of the material surface.
Image Credit: ©T. Imamura, Y. Maejima, K. Sugiyama et al., 2026
(CC BY 4.0)

A team including researchers from the University of Tokyo has revealed the mysterious origin of an impressive cloud disturbance on Venus. Researchers used numerical models to demonstrate that an enormous, 6,000-kilometer-wide atmospheric wavefront, which circumnavigates the planet for days at a time, is caused by a large "hydraulic jump." A hydraulic jump occurs 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 exploratory missions.

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

A key feature of Venusian clouds is that they "superrotate," moving about 60 times faster than the planet turns. Researchers 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 kilometers wide—repeatedly sweeps around the planet's equator.

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

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

Hydraulic jump in a kitchen sink. In this image, the clearly defined hydraulic jump can be seen in the difference between the smooth inner circle of shallow and fast water, and the ripples of deeper, slower water beyond.
Photo Credit: ©Takeshi Imamura 2026
(CC BY 4.0)

The hydraulic jump on Venus occurs when an eastward-moving atmospheric wave, known as a Kelvin wave, in the lower to middle cloud region suddenly becomes unstable. The wind speed, relative to the atmospheric wave, abruptly slows down, and a strong localized updraft is created, carrying sulfuric acid vapor higher into the atmosphere. The droplets condense into clouds that trail behind, creating the massive wavefront that can be seen sweeping around the planet.

"Venus has three distinct cloud layers, and the dynamics of the lower and middle layers are not 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 dynamics model (a numerical analysis that simulates how gases or liquids flow), and the cloud formation was studied using a microphysical box model (which follows the behavior of an example section of air as it moves through the atmosphere). In addition to simulating the cloud disturbance, the team found that this process helps maintain the superrotation of Venus's atmosphere.

"Until now, we used a global circulation model (GCM) for Venus that is similar to Earth's, but this model does not include the hydraulic jump that we have now identified," explained Imamura. "Our next step will be to test this discovery within a more inclusive climate model that incorporates other atmospheric processes. We will face challenges due to the huge amount of processing power required to run such simulations. Even with modern supercomputers, it is not 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's atmosphere may also have the right conditions for a hydraulic jump," mentioned Imamura. Creating more accurate models of atmospheric conditions will aid the success of future missions to Mars, as well as wider space exploration.

Published in journal: Journal of Geophysical Research: Planets

Title: A Planetary-Scale Hydraulic Jump Driving Venus' Cloud Front

Authors: Takeshi Imamura, Yasumitsu Maejima, Ko-ichiro Sugiyama, Takehiko Satoh, Javier Peralta, Kevin McGouldrick, Takeshi Horinouchi, and Kohei Ikeda

Source/Credit: University of Tokyo

Reference Number: ps051026_01

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