Exploring the Venusian Clouds: Dayside Atmospheric Gravity Waves with Akatsuki UVI instrument

As our neighbouring world, Venus stands as a pivotal planet in the study of planetary evolution. Its dense atmosphere, mostly composed of carbon dioxide makes it a unique laboratory for understanding terrestrial type planets with extreme greenhouse effect., not only within the solar system, but also beyond its boundaries. One of the most intriguing features of Venus’ atmosphere is its circulation, dominated by retrograde zonal winds which superrotate much faster than the planet itself and whose mechanisms are yet poorly understood.
Atmospheric gravity waves, oscillatory disturbances that propagate through stable stratified atmospheres, play a crucial role in the global circulation of a planet's atmosphere. These waves facilitate the horizontal and vertical transfer of energy, momentum, and chemical species, powering the weather system of the planet. Numerous studies have confirmed the presence of gravity waves across various wavelength ranges within Venus's atmosphere [1,2,3,4], meticulously mapping their behavior across the cloud deck. However, many questions remain unsolved and further research is needed to fully understand the impact of these waves on the Venusian atmosphere. In short, the study of atmospheric gravity waves is fundamental in deciphering the mechanisms behind phenomena like Venus's superrotation.
With this work we use observations from Akatsuki's Ultraviolet Imager (UVI) to search for wave-like structures on the dayside of Venus. Through analyzing data from Akatsuki's public database, we aim to assess the population of atmospheric waves, measuring their physical and dynamical properties, including crest number, horizontal wavelength, packet length, width, and orientation. We will also investigate their local time dependence and oscillation frequency in order to better constrain the role of atmospheric convection as an excitation source for these waves This research builds upon previous studies by Peralta et al. (2008)[1] and Silva et al. (2021)[3,4], furthering our understanding of atmospheric dynamics on Venus and shedding light on the mechanisms which drive it.

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.

[1] Peralta et al., Characterization of mesoscale gravity waves in the upper and lower clouds of venus from vex-virtis images. Journal of Geophysical Research: Planets, 113(E5), 2008.
[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.