Dependency of the vertical propagation of mountain waves on the zonal wind and the static stability in the lower Venusian atmosphere

Abstract

Long-Infrared camera (LIR) onboard Akatsuki have detected bow-shaped features over mountain regions, suggesting that mountain waves propagate upward to reach the cloud top level. In this study, we investigated how the vertical propagation characteristics of the mountain waves depend on the thickness and static stability of the planetary boundary layer and the zonal wind near the surface by using a two-dimensional non-hydrostatic model. The obtained results were compared with the observations mainly at the cloud top level. The amplitude of waves reproduced in the model is comparable to the observations at the cloud top level when the zonal wind near the surface is relatively fast and the top of the planetary boundary layer is lower than the top of the mountain. The wave amplitude also becomes comparable to the observations when the top of the planetary boundary layer is higher than the top of the mountain, while it depends also on the zonal wind speed near the surface and the static stability in the planetary boundary layer. Our results suggest that the zonal wind speed and the atmospheric structure near the surface vary with local time and might be able to explain why the bow-shaped structure is often seen in the evening time.