Key Driver of Extreme Winds on Venus Identified
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Venus is known for having extreme weather conditions on its surface. | Credit: NASA
This article was originally published on Eos. The publication contributed the article to Space.com Expert voices: opinion pieces and perspectives.
Imagine the catastrophic winds of a Category 5 hurricane. Now imagine even faster winds, over 100 meters per second, encircling the planet and sweeping clouds across the sky, with no end in sight. This scenario would be surprising Earth, but it’s the usual Venus, where the atmosphere at cloud level revolves around 60 times faster than the planet itself – a phenomenon known as superrotation. In contrast, Earth’s cloudy atmosphere rotates at about the same speed as the planet’s surface.
Previous research has explored the mechanisms behind atmospheric superrotation on Venus, but the details remain obscure. New evidence of Lai et al. suggests that a once-daily atmospheric tidal cycle, fueled by heat from the sun, contributes much more to the planet’s extreme winds than previously thought.
Rapid atmospheric rotation often occurs on rocky planets that, like Venus, are located relatively close to their stars and rotate very slowly. On Venus, a complete rotation takes 243 Earth days. During this time, the atmosphere circles the planet in just 4 Earth days.
To better understand this superrotation, researchers analyzed data collected between 2006 and 2022 by the European Space Agency. Venus Express satellite and the Japan Aerospace Exploration Agency satellite Akatsuki satellite, both of which studied the atmosphere of Venus by detecting how it bends radio waves. The research team also simulated superrotation using a numerical model of the atmosphere of Venus.
The analysis focused specifically on thermal tides, one of several atmospheric processes, alongside southern circulation And planetary waveswhose interactions have already been shown to support the superrotation of Venus by carrying momentum. Thermal tides are air movements that occur when sunlight warms the air on the dayside of a planet. Venusian thermal tides can be divided into two main components: diurnal tides, which follow a cyclical pattern repeating once per Venusian day, and semidiurnal tides, which have two cycles per day.
Previous research suggested that semidiurnal tides were the main component of thermal tides involved in superrotation. However, this study, which includes the first analysis of thermal tides in Venus’ southern hemisphere, found that diurnal tides play a primary role in transporting momentum to the tops of Venus’ thick clouds, suggesting that diurnal tides are a large contributor to the fast winds.
Although the researchers note that further clarification of the contributions of diurnal tides is needed, the work sheds new light on Venus’ extreme winds and could facilitate meteorological research on other slowly rotating planets.
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