Super-rotation independent of horizontal diffusion reproduced in a Venus GCM

Abstract

Horizontal diffusion and resolution are important factors to generate and maintain the super-rotation in the general circulation model (GCM) because waves which transport angular momentum are sensitive to them. Here, we investigated how the super-rotation depends on the magnitude of horizontal hyper diffusion using a Venus atmospheric GCM with medium and high resolutions. In both the runs, we found a parameter range where the structure of fully developed super-rotation is almost independent of the magnitude of horizontal diffusion. Spectral analysis shows that unrealistically strong super-rotation is developed when medium-scale disturbances are dissipated by stronger horizontal diffusion. On the other hand, artificially weak super-rotation is also realized because spurious small-scale disturbances are accumulated when the horizontal diffusion is too weak. Graphical Abstract

Formation and Quasi‐Periodic Variation of Equatorial Jet Caused by Planetary‐Scale Waves in the Venusian Lower Cloud Layer

“…See the work of Sugimoto et al. (2023) for a discussion of how the model depends on the horizontal hyperviscosity. The vertical eddy diffusion is also used in the model, whose coefficient is fixed to be 0.0015 $${{\mathrm{m}}^{\mathrm{2}}\,\mathrm{s}}^{-1}$$ (Sugimoto et al., 2019).…”

“…The horizontal eddy diffusion is represented by second-order hyperviscosity with a relaxation time of about 1 day for the largest wavenumber components. See the work of Sugimoto et al (2023) for a discussion of how the model depends on the horizontal hyperviscosity. The vertical eddy diffusion is also used in the model, whose coefficient is fixed to be 0.0015 𝐴𝐴 m 2 s −1 (Sugimoto et al, 2019).…”