Presentation Information
[PPS08-P11]Long Term Variability of Super-Rotation Reproduced by Akatsuki Horizontal Wind Assimilation★Invited Papers
*Yukiko Fujisawa1, Norihiko Sugimoto1, Nobumasa Komori1, Shin-ya Murakami2, Hiroki Ando3, Masahiro Takagi3, Takeshi Imamura4, Takeshi Horinouchi5, George HASHIMOTO6, Masaki Ishiwatari5, Takeshi Enomoto7, Takemasa Miyoshi8, Hiroki Kashimura6, Yoshi-Yuki Hayashi6 (1.Keio University, 2.Japan Aerospace Exploration Agency, 3.Kyoto Sangyo University, 4.The University of Tokyo, 5.Hokkaido University, 6.Kobe University, 7.Kyoto University, 8.RIKEN Center for Computational Science)
Keywords:
Venus atmosphere,Data assimilation,Akatsuki
In Fujisawa et al. (2022) [1], we previously produced an objective analysis of the Venusian atmosphere by assimilating horizontal winds derived from cloud tracking of the UVI camera onboard the Venus orbiter Akatsuki. To produce objective analysis, we used the Venus atmospheric data assimilation system ALEDAS-V (Sugimoto et al., 2017) [2], which is based on the Venus general circulation model AFES-Venus (Sugimoto et al., 2014) [3]. This dataset appropriately corrects both the phase bias of thermal tides and the super-rotation speed in AFES-Venus to be closer to those observed in the real Venusian atmosphere. The dataset was produced by assimilating observations from September to December 2018, a period that includes an intensive observation period of Akatsuki.
Akatsuki has accumulated observational data over a long period from 2015 to 2024, and it has been revealed that the super-rotation speed exhibits both faster and slower periods (Horinouchi et al., 2024) [4]. In this study, we selected five epochs during the Akatsuki observation period that exhibit characteristic super-rotation speeds and performed data assimilation for each epoch. The figure shows the super-rotation speed for each epoch, defined as the zonal-mean zonal wind at an altitude of 69 km. Compared with the free-run experiment without data assimilation (frf), the super-rotation speeds in each epoch with assimilated observations are significantly reduced, and we confirm that speeds close to the observations, including their meridional asymmetry, are successfully reproduced. In this presentation, we will show the relationship between the reproduced super-rotation speeds and the structure of the atmospheric circulation.
[1] Fujisawa, Y., et al. (2022) Sci. Rep. 12, 14577.
[2] Sugimoto, N., et al. (2017) Sci. Rep. 7(1), 9321.
[3] Sugimoto, N., et al. (2014) J. Geophys. Res. Planets 119, 1950–1968.
[4] Horinouchi, T., et al. (2024) J. Geophys. Res. Planets 129, e2023JE008221.
Akatsuki has accumulated observational data over a long period from 2015 to 2024, and it has been revealed that the super-rotation speed exhibits both faster and slower periods (Horinouchi et al., 2024) [4]. In this study, we selected five epochs during the Akatsuki observation period that exhibit characteristic super-rotation speeds and performed data assimilation for each epoch. The figure shows the super-rotation speed for each epoch, defined as the zonal-mean zonal wind at an altitude of 69 km. Compared with the free-run experiment without data assimilation (frf), the super-rotation speeds in each epoch with assimilated observations are significantly reduced, and we confirm that speeds close to the observations, including their meridional asymmetry, are successfully reproduced. In this presentation, we will show the relationship between the reproduced super-rotation speeds and the structure of the atmospheric circulation.
[1] Fujisawa, Y., et al. (2022) Sci. Rep. 12, 14577.
[2] Sugimoto, N., et al. (2017) Sci. Rep. 7(1), 9321.
[3] Sugimoto, N., et al. (2014) J. Geophys. Res. Planets 119, 1950–1968.
[4] Horinouchi, T., et al. (2024) J. Geophys. Res. Planets 129, e2023JE008221.