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- Title
Planetary‐Scale Waves Seen in Thermal Infrared Images of Venusian Cloud Top.
- Authors
Kajiwara, Naoya; Imamura, Takeshi; Taguchi, Makoto; Kouyama, Toru
- Abstract
Planetary‐scale waves are thought to play a crucial role in the maintenance of the atmospheric circulation of Venus. They have been mainly studied using ultraviolet images. In this study, cloud top temperature oscillations associated with planetary‐scale waves were extracted from thermal images taken over 142 Earth days by the Longwave Infrared Camera onboard JAXA's Akatsuki spacecraft. A spectral analysis showed that multiple planetary‐scale waves overlap. The latitudinal structures of four distinct waves with periods of 3.6, 5.0, 5.4, and 6.1 days were studied. The 3.6‐day wave is considered to be a Kelvin wave and the other waves are considered to be hemispherically symmetric Rossby waves. Although the Rossby waves have similar periods, their latitudinal structures are different. The Rossby waves are considered to originate from different sources based on a comparison with analytical solutions. Plain Language Summary: The motion of the Venus's atmosphere is dominated by a global‐scale westward wind in a superrotation state. Momentum transport by planetary‐scale waves may help maintain the superrotation. The characteristics of such waves are not well‐known. Here, we use the cloud top temperature data taken by a thermal imager onboard JAXA's Akatsuki spacecraft to detect planetary‐scale waves at the cloud top. A spectral analysis identified multiple waves that exist simultaneously. The structures of four waves with periods of 3.6, 5.0, 5.4, and 6.1 Earth days were studied. The 3.6‐day wave will be a Kelvin wave, and the other waves will be Rossby wave. The structures of the Rossby waves were investigated based on a comparison with theoretical wave solutions. It is supposed that the observed Rossby waves originate from different wave sources. Key Points: Planetary‐scale waves were observed at the Venusian cloud top in thermal infrared images taken by the Venus orbiter AkatsukiFour distinct modes were identified in the spectra; one is attributed to a Kelvin wave and the others are attributed to Rossby wavesThe Rossby waves are thought to originate in different regions based on a comparison with analytical solutions
- Subjects
ATMOSPHERIC circulation; WAVES (Physics); VENUSIAN atmosphere; CLOUDS; INFRARED cameras
- Publication
Journal of Geophysical Research. Planets, 2021, Vol 126, Issue 12, p1
- ISSN
2169-9097
- Publication type
Article
- DOI
10.1029/2021JE007047