3:30 PM - 3:45 PM
[ACG47-13] Kelvin and Rossby wave coupling in a Venus GCM
★Invited Papers
Keywords:Kelvin wave , Rossby wave , Venus
Planetary-scale Kelvin-like gravity waves and Rossby waves with short periods of <10 Earth days and long periods of 117 and 58.5 Earth days have been observed in the Venus cloud layer between 50 and 70 km height, where the super-rotation of 4-8 Earth days have been driven. Some horizontal structures of Kelvin and Rossby waves with the same phase velocity are similar to the Matsuno-Gill response seen on Earth and tidally-locked planets. In this presentation, we will overview the dynamics of the Kelvin and Rossby wave coupling in a Venus general circulation model (GCM) developed at the Atmosphere and Ocean Research Institute, the University of Tokyo (AORI), based on the divergent/rotational wind structures and energetics (Yamamoto et al. 2023, 2024).
The most predominant short-period waves (7.5 Earth day waves in our GCM) are composed of three types: a Rossby wave in the upper cloud layer, a Rossby wave around the polar tropopause, and an equatorial Kelvin-like wave around and below the cloud bottom (Yamamoto et al. 2023). They are formed and maintained by the baroclinic and barotropic energy conversions in the vicinity of the critical line. We can see that the Kelvin and Rossby waves are separated at the critical latitude near the cloud bottom (~50 km), but they are horizontally jointed with the stream function and velocity potential at the critical latitude. The pair of the Kelvin and Rossby waves near the cloud bottom is a major equatorward momentum transporter contributing to the super-rotation and is generated by horizontal shear (or barotropic) and baroclinic instabilities associated with energy conversion at the critical line. The equatorial super-rotational flow is accelerated by the rotational zonal flow and meridional divergence and by the meridionally-tilting stream function around the equator (Yamamoto et al. 2023).
The solar-locked long-period waves (i.e., thermal tides) have the horizontal structures of thermally-forced Kelvin-like gravity waves at low latitudes and tidal gyres such as Rossby waves at high latitudes (Yamamoto et al. 2024). The divergent flows are thermally forced at the maximum heating area around the cloud top (~65 km), where diabatic heating generates eddy available potential energy. The tidal gyres are formed in mid- and high-latitude regions, where diurnal barotropic energy conversion occurs around the zonal-mean jet core and semidiurnal baroclinic energy conversion occurs below the cloud layer far from the solar heating maximum (Yamamoto et al. 2024).
As the pairs of the Kelvin and Rossby waves have been seen in other planetary GCMs, the divergent/rotational wind structures and energetics of the three-dimensional Matsuno-Gill response forced by the solar heating and Kelvin-Rossby instability could be important in discussing the dynamical coupling between Kelvin-like and Rossby waves in the planetary super-rotations.
Acknowledgments: This study was supported by the cooperative research activities of the collaborative use of the computing facility of AORI and the MEXT/JSPS KAKENHI grant (Grant Number JP23K03492).
The most predominant short-period waves (7.5 Earth day waves in our GCM) are composed of three types: a Rossby wave in the upper cloud layer, a Rossby wave around the polar tropopause, and an equatorial Kelvin-like wave around and below the cloud bottom (Yamamoto et al. 2023). They are formed and maintained by the baroclinic and barotropic energy conversions in the vicinity of the critical line. We can see that the Kelvin and Rossby waves are separated at the critical latitude near the cloud bottom (~50 km), but they are horizontally jointed with the stream function and velocity potential at the critical latitude. The pair of the Kelvin and Rossby waves near the cloud bottom is a major equatorward momentum transporter contributing to the super-rotation and is generated by horizontal shear (or barotropic) and baroclinic instabilities associated with energy conversion at the critical line. The equatorial super-rotational flow is accelerated by the rotational zonal flow and meridional divergence and by the meridionally-tilting stream function around the equator (Yamamoto et al. 2023).
The solar-locked long-period waves (i.e., thermal tides) have the horizontal structures of thermally-forced Kelvin-like gravity waves at low latitudes and tidal gyres such as Rossby waves at high latitudes (Yamamoto et al. 2024). The divergent flows are thermally forced at the maximum heating area around the cloud top (~65 km), where diabatic heating generates eddy available potential energy. The tidal gyres are formed in mid- and high-latitude regions, where diurnal barotropic energy conversion occurs around the zonal-mean jet core and semidiurnal baroclinic energy conversion occurs below the cloud layer far from the solar heating maximum (Yamamoto et al. 2024).
As the pairs of the Kelvin and Rossby waves have been seen in other planetary GCMs, the divergent/rotational wind structures and energetics of the three-dimensional Matsuno-Gill response forced by the solar heating and Kelvin-Rossby instability could be important in discussing the dynamical coupling between Kelvin-like and Rossby waves in the planetary super-rotations.
Acknowledgments: This study was supported by the cooperative research activities of the collaborative use of the computing facility of AORI and the MEXT/JSPS KAKENHI grant (Grant Number JP23K03492).