Reproduction of Long-Term Variability of Super-Rotation Using Akatsuki Horizontal Wind Data Assimilation

Yukiko Fujisawa; Norihiko Sugimoto; Nobumasa Komori; Shin-ya Murakami; Hiroki Ando; Masahiro Takagi; Takeshi Imamura; Takeshi Horinouchi; George L. Hashimoto; Masaki Ishiwatari; Takeshi Enomoto; Takemasa Miyoshi; Hiroki Kashimura; Yoshi-Yuki Hayashi

doi:https://doi.org/10.5194/egusphere-egu26-3726

[Back] [Session VPS27]

EGU26-3726, updated on 13 Mar 2026

https://doi.org/10.5194/egusphere-egu26-3726

EGU General Assembly 2026

© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.

Oral | Monday, 04 May, 14:00–14:03 (CEST)

vPoster spot 4

Poster | Monday, 04 May, 16:15–18:00 (CEST), Display time Monday, 04 May, 14:00–18:00

vPoster Discussion, vP.43

Reproduction of Long-Term Variability of Super-Rotation Using Akatsuki Horizontal Wind Data Assimilation

Yukiko Fujisawa¹, Norihiko Sugimoto¹, Nobumasa Komori¹, Shin-ya Murakami², Hiroki Ando³, Masahiro Takagi³, Takeshi Imamura⁴, Takeshi Horinouchi⁵, George L. Hashimoto⁶, Masaki Ishiwatari⁵, Takeshi Enomoto⁷, Takemasa Miyoshi⁸, Hiroki Kashimura⁶, and Yoshi-Yuki Hayashi⁶

Yukiko Fujisawa et al.

¹Keio University, Yokohama, Japan
²Japan Aerospace Exploration Agency, Sagamihara, Japan
³Kyoto Sangyo University, Kyoto, Japan
⁴The University of Tokyo, Tokyo, Japan
⁵Hokkaido University, Sapporo, Japan
⁶Kobe University, Kobe, Japan
⁷Kyoto University, Kyoto, Japan
⁸RIKEN Center for Computational Science, Kobe, Japan

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. As a result, we confirmed that distinct super-rotation speeds corresponding to each epoch, including their meridional asymmetry, are reproduced. In the 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.

How to cite: Fujisawa, Y., Sugimoto, N., Komori, N., Murakami, S., Ando, H., Takagi, M., Imamura, T., Horinouchi, T., Hashimoto, G. L., Ishiwatari, M., Enomoto, T., Miyoshi, T., Kashimura, H., and Hayashi, Y.-Y.: Reproduction of Long-Term Variability of Super-Rotation Using Akatsuki Horizontal Wind Data Assimilation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3726, https://doi.org/10.5194/egusphere-egu26-3726, 2026.