[P-PS05] Recent advances of Venus science

[PPS05-04] Atmospheric structures simulated by T21 and T63 Venus GCMs with radiative transfer

*Masaru Yamamoto¹, Kohei Ikeda², Masaaki Takahashi² (1.Research Institute for Applied Mechanics, Kyushu University, 2.National Institute for Environmental Studies)

Radiative forcing and topography are important in the formations of the thermal and wind structures on Venus. The surface topography forces stationary waves, which induce large-scale stationary bow-shaped wave pattern (Fukuhara et al. 2017) and conspicuous variation of cloud-top zonal flow (Bertaux et al. 2016) over the Aphrodite Terra. The topographical and radiative effects on Venus’ atmosphere general circulation have been investigated using a T21L52 Venus AGCM at Atmosphere and Ocean Research Institute, Univ. Tokyo (Ikeda 2011). Our Venus GCM with the topographical data and radiative code simulated solar-locked and geographical atmospheric structures on Venus (Yamamoto et al. 2019). The model reproduced the wind structure near the subsolar point and the slowness of zonal wind over the Aphrodite Terra. Furthermore it showed that (1) the sub-rotation is formed near the surface in and around high land and mountains, (2) weakly stable layer is formed at 10-20 km at low latitudes, and (3) the zonal wind is weakened at the cloud top over the Aphrodite Terra. The third result implies that the negative wind deviation of the topographically forced stationary wave produces the slowness of the cloud-top zonal wind around the Aphrodite Terra. The GCM with the radiative code estimated the heat budget in the lower and middle atmospheres and reproduced the static stability similar to the observation. For the simulated zonal-mean structure, an equatorial fast flow of ∼90 m/s and mid-latitude jets of ∼120 m/s are formed around the cloud top. A poleward flow of >8 m/s is formed above the cloud layer, where the imbalance between solar and infrared radiative heating is large. Around the cloud top where the solar radiative heating balances the infrared one, a poleward flow is small (∼1 m/s) and confined within the equatorward flank of the jet core. In and around the jet core, indirect circulations are formed by the eddy heat fluxes owing to the thermal tide and baroclinic waves. In solar-fixed coordinates, differences are significant between the zonal and dayside averages of the meridional wind and its related fluxes within the cloud layer. This suggests that we must carefully estimate the zonal-mean Hadley circulation, eddy momentum flux, and eddy heat flux from the one-side hemisphere. Most of the abovementioned features obtained from the T21 GCM are also seen in the T63 GCM. In this presentation, under the realistic thermal and topographical condition, the effects of the high resolution are also discussed. If we have room or time in this presentation, we briefly show the momentum budget, together with the heat budget shown in Yamamoto et al. (2019).