Morphological and dynamical characterisation of Gravity Waves on Venus’ atmosphere using Akatsuki´s UVI instrument

Amidst the planets of our Solar System, Venus remains one of the most intriguing subjects of scientific interest. Despite its many similarities with our home planet Earth, the evolution of this planet followed a path that resulted in a world vastly different from its neighbouring planet. Among the well-known characteristics that make Venus so unique, such as the slow rotation rate or the extreme surface temperature, its atmosphere is, without a doubt, one of the most striking. The Venusian atmosphere is a dense and inhospitable mixture primarily composed of carbon dioxide, with thick clouds of sulfuric acid. It also exhibits superrotation, where winds move much faster than the planet's rotation. To fully understand the dynamics of Venus clouds, the study of atmospheric gravity waves is a crucial step.

Atmospheric gravity waves are periodic oscillatory disturbances driven by buoyancy which are critical components in the global circulation of planetary atmospheres. These waves, which require a stably stratified atmosphere to propagate, facilitate the transfer of energy, momentum, and chemical species, significantly impacting weather systems. On Venus, atmospheric gravity waves play an essential role in the dynamics of its atmosphere. Despite previous studies that have mapped the presence of these waves in various wavelengths across Venus's cloud deck, many aspects remain poorly understood, particularly their role in driving the planet’s superrotation.

This work leverages observations from Akatsuki’s Ultraviolet Imager (UVI) to explore wave-like structures on the dayside of Venus's atmosphere at a wavelength of 365 nm. By analyzing data from Akatsuki’s public database, we aim to characterize the population of atmospheric gravity waves, measuring their physical properties (e.g., crest number, horizontal wavelength, packet length, width, and orientation) and dynamical characteristics such as the intrinsic phase velocity and vertical wavelength). Additionally, we will investigate the local time dependence and oscillation frequencies of these waves to understand their excitation sources, including atmospheric convection. This research builds on previous studies by Peralta et al. (2008), Silva et al. (2021) and Silva et al. (2024), advancing our understanding of Venus’s atmosphere and the mechanisms underlying its dynamics.

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[2] Piccialli et al., High latitude gravity waves at the venus cloud tops as observed by the venus monitoring camera on board venus express. Icarus, 227:94 111, 01 2014.
[3] Silva et al., Characterising atmospheric gravity waves on the nightside lower clouds of Venus: a systematic analysis, AA 649 A34, 2021.
[4] Silva et al., Atmospheric gravity waves in Venus dayside clouds from VIRTIS-M images, Icarus, Volume 415, 2024, 116076, ISSN 0019-1035.

Acknowledgements: This work was supported by the Portuguese Fundação Para a Ciência e a Tecnologia of reference PTDC/FIS-AST/29942/2017, through national funds and by FEDER through COMPETE 2020 of reference POCI-01-0145-FEDER-007672, and through a grant of reference 2020.06389.BD.