[P-PS04] Recent advances in the science of Venus

[PPS04-09] Rossby wave and its impact on the Venus atmosphere evaluated by observing system simulation experiment

*小守 信正¹、杉本 憲彦¹、藤澤 由貴子¹、阿部 未来²、神山 徹³、安藤 紘基⁴、高木 征弘⁴、山本 勝⁵ (1.慶應義塾大学、2.横浜国立大学、3.産業技術総合研究所、4.京都産業大学、5.九州大学)

キーワード：金星大気、ロスビー波、データ同化、スーパーローテーション、観測システムシミュレーション実験

At the cloud top of the Venus atmosphere, mid-latitude Rossby waves have been observed and are considered to play an important role in the maintenance of the super-rotation. We were able to reproduce the waves in a general circulation model named AFES-Venus (Sugimoto et al., 2014) by conducting an observing system simulation experiment with the help of a data assimilation technique (ALEDAS-V; Sugimoto et al., 2017). The synthetic observations of horizontal winds associated with the Rossby wave are produced by a linear wave propagation model, and they are assimilated at the cloud top (∼70 km) for 30 Earth days in realistic conditions, assuming they are obtained from cloud tracking of ultra-violet images taken by the Venus orbiters. It is demonstrated using Eliassen–Palm fluxes that enhanced Rossby wave in the mid-latitudes induces a deceleration in zonal-mean zonal wind. After the stop of data assimilation, the model fields reached another quasi-equilibrium state within about 10 Earth days, indicating that the “memory” of assimilated observations can be kept for a while even new observations are not available.

Sugimoto, N., M. Takagi, and Y. Matsuda (2014): Baroclinic instability in the Venus atmosphere simulated by GCM. J. Geophys. Res.: Planets, 119 (8), 1950–1968, doi:10.1002/2014JE004624.
Sugimoto, N., A. Yamazaki, T. Kouyama, H. Kashimura, T. Enomoto, and M. Takagi (2017): Development of an ensemble Kalman filter data assimilation system for the Venusian atmosphere. Sci. Rep., 7, 9321, doi:10.1038/s41598-017-09461-1.