日本地球惑星科学連合2023年大会

講演情報

[E] オンラインポスター発表

セッション記号 P (宇宙惑星科学) » P-PS 惑星科学

[P-PS04] Advancing the science of Venus in the golden age of exploration

2023年5月25日(木) 09:00 〜 10:30 オンラインポスターZoom会場 (2) (オンラインポスター)

コンビーナ:佐藤 毅彦(宇宙航空研究開発機構・宇宙科学研究本部)、はしもと じょーじ(岡山大学学術研究院自然科学学域)、Moa Persson(Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan)、Kevin McGouldrick(University of Colorado Boulder)



現地ポスター発表開催日時 (2023/5/23 17:15-18:45)

09:00 〜 10:30

[PPS04-P16] Latitudinal and vertical structures of Venusian planetary-scale waves and their temporal variation studied with Akatsuki LIR

小山 裕幸1,5、*今村 剛1田口 真2神山 徹3佐藤 隆雄4 (1.東京大学大学院 新領域創成科学研究科、2.立教大学 理学部、3.産業技術総合研究所、4.北海道情報大学、5.東京大学大学院 理学系研究科)

キーワード:金星、大気波動、あかつき

The contribution of planetary-scale waves such as Rossby and Kelvin waves to the maintenance of the superrotation of the Venusian atmosphere is under debate. While model calculations predict contribution of such waves, observational constraints on the three-dimensional structures of the waves and the interaction between these waves and the mean flow are not enough. In this study, we obtain wave spectra from the variation of the cloud-top temperature over a period of 10 Venus years using the brightness temperature data obtained by the Longwave Infrared Camera (LIR) onboard Akatsuki. The latitudinal structures of the waves were compared with that of the background wind, and the temporal variations of the wave periods were also compared with that of the background wind. Near the cloud tops, waves with a period of about 4 days, which propagates faster than the background wind, and waves with a period of 5-6 days, which propagates slower than the background wind, are observed; the former waves will be Kelvin waves, while the latter, Rossby waves. Multiple spectral peaks are observed both for Kelvin and Rossby waves. Though the 5- to 6-day period Rossby waves usually have amplitude maxima at mid-latitudes of both hemispheres, they frequently exhibit additional amplitude maxima near the equator especially when the emission angle of the observation is small. Considering that the contribution function of LIR extends to lower altitudes for smaller emission angles, this result suggests the possibility that coupled Rossby-Kelvin modes arise at altitudes below the cloud top. It was also found that the periods of the planetary-scale waves change with the variation of the period of the background wind at the cloud top. This might be explained by the local excitation of the waves near the cloud top or by the selective attenuation of the vertically-propagating waves excited in the lower atmosphere with periods close to that of the background wind.