Wave Packets at Venus’ Cloud Tops as seen by Akatsuki

As our neighbouring world, Venus stands as a key planet in the study of planetary evolution. Its extreme climate and dense atmosphere composed of mainly carbon dioxide make it a unique environment for understanding atmospheric dynamics, not only within the solar system, but also beyond its boundaries. Among its most remarkable atmospheric features is superrotation, where zonal winds circulate far more rapidly than the planet’s rotation. Understanding the mechanisms that sustain this and other phenomena remains a challenge in planetary science, and atmospheric gravity waves are thought to play a role in shaping a planet’s atmospheric circulation.

Atmospheric gravity waves (AGW) are oscillations that propagate in stably stratified atmospheres, redistributing energy and momentum and influencing large-scale circulation patterns. In this study, we investigate wave activity in the upper cloud layer of Venus using ultraviolet images acquired by the Ultraviolet Imager (UVI) onboard the Akatsuki spacecraft. By applying contrast enhancement techniques and geometric corrections to a subset of the publicly available dataset, we identify and analyse wave packets across the dayside cloud tops. We then derive their morphological characteristics, including horizontal wavelength, packet length, width, and orientation, alongside dynamical parameters such as intrinsic phase velocity and vertical wavelength [2, 4]. These measurements are complemented by comparisons with independent measurements from thermal profiles obtained via Akatsuki’s radio occultation experiments [6], as well as earlier observations from Venus Express instruments [1, 3, 5].

Overall, this study provides the first comprehensive characterization of bow wave populations at Venus’s cloud tops using ultraviolet imaging. The findings offer new constraints on the properties and distribution of atmospheric gravity waves and contribute to ongoing efforts to clarify their possible role in maintaining Venusian superrotation.

 

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