[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

*Nobumasa Komori¹, Norihiko Sugimoto¹, Yukiko Fujisawa¹, Mirai Abe², Toru Kouyama³, Hiroki Ando⁴, Masahiro Takagi⁴, Masaru Yamamoto⁵ (1.Keio University, 2.Yokohama National University, 3.National Institute of Advanced Industrial Science and Technology, 4.Kyoto Sangyo University, 5.Kyushu University)

Keywords:Venus atmosphere, Rossby wave, data assimilation, super-rotation, observing system simulation experiment

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.