Diurnal Thermal Tides Power Venus’s Furious Superrotation, Study Finds

Imagine the force of a category 5 hurricane — then picture winds even stronger, exceeding 100 meters per second, sweeping clouds continuously around an entire world. That is routine on Venus, where the atmosphere at cloud level rotates roughly 60 times faster than the solid planet in a phenomenon known as superrotation.

Venus itself completes one rotation in 243 Earth days, yet its cloud-level atmosphere circles the planet in about 4 Earth days. Understanding what sustains that dramatic difference has been a long-standing puzzle in planetary meteorology.

New analysis led by Lai et al. combines observations and numerical simulations to show that once-per-Venus-day thermal tides — diurnal tides driven by solar heating — play a far larger role in fueling superrotation than previously believed.

The team examined radio-occultation measurements taken between 2006 and 2022 by the European Space Agency's Venus Express and the Japan Aerospace Exploration Agency's Akatsuki missions. Both missions probed Venus’s atmosphere by observing how it refracts and bends radio signals from spacecraft, providing vertical profiles of temperature, density and winds. The researchers also reproduced atmospheric behavior using a numerical climate model of Venus.

Thermal tides are global atmospheric oscillations created when sunlight heats the dayside atmosphere. On Venus these tides separate into diurnal components (one cycle per Venus day) and semidiurnal components (two cycles per day). Previous work emphasized semidiurnal tides as the dominant thermal-tide contributor to superrotation.

However, this study — which includes the first comprehensive analysis of thermal tides in Venus's southern hemisphere — finds that diurnal tides efficiently transport angular momentum upward toward the tops of the planet’s dense cloud layers. That upward momentum pumping helps accelerate winds at cloud level and therefore is a major contributor to the observed superrotation.

The authors note that meridional circulation and planetary waves also interact with thermal tides to sustain the full superrotating state, and that additional study is needed to precisely quantify the relative contributions of diurnal and semidiurnal tides. Still, these results shift the balance of evidence toward a stronger role for once-per-day solar forcing in powering Venus’s extreme winds.

Why it matters: Clarifying how thermal tides drive superrotation improves our understanding of atmospheric dynamics on slowly rotating rocky planets and can inform interpretation of observations and models for Venus and for exoplanets in similar regimes. Future missions and targeted modeling will help refine the quantitative impact of diurnal tides.