A general circulation model ensemble study of the atmospheric circulation of Venus

Abstract

[1] The response of three numerical model dynamical cores to Venus-like forcing and friction is described in this paper. Each dynamical core simulates a super-rotating atmospheric circulation with equatorial winds of 35 ± 10 m/s, maintained by horizontally propagating eddies leaving the equatorial region and inducing a momentum convergence there. We discuss the balance between the mean circulation and eddies with reference to the production of a super-rotating equatorial flow. The balance between the horizontal eddies and vertical eddies in the polar region is discussed and shown to produce an indirect overturning circulation above the jet. The indirect overturning may be related to the observed region of the polar dipole in the Venus atmosphere. Reservoirs of energy and momentum are calculated for each dynamical core and explicit sources and sinks are diagnosed from the general circulation model (GCM). The effect of a strong "sponge layer" damping to rest is compared with eddy damping and found to change significantly the momentum balance within the top "sponge layer" but does not significantly affect the super-rotation of the bulk of the atmosphere. The Lorenz (1955) energy cycle is calculated and the circulation is shown to be dominated by energy conversion between the mean potential energy and mean kinetic energy reservoirs, with barotropic energy conversion between the mean kinetic energy and eddy kinetic energy reservoirs. We suggest modifications to the GCM parameterizations on the basis of our analysis of the atmospheric circulation and discuss the effect of numerical parameterizations on the simulated atmosphere.Citation: Lee, C., and M. I. Richardson (2010), A general circulation model ensemble study of the atmospheric circulation of Venus,

Possible climates on terrestrial exoplanets

“…An interesting case is the Venus general circulation-the super-rotation of Venus atmosphere is the result of a subtle equilibrium involving balance in the exchanges of angular momentum between surface and atmosphere, and balance in the angular momentum transport between the mean meridional circulation and the planetary waves, thermal tides and gravity waves. Comparative studies between Venus GCMs under identical physical forcings [99,100] have recently shown that modelling this balance is extremely sensitive to the dynamical core details, to the boundary conditions and possibly also to initial conditions. These studies revealed that various dynamical cores, which would give very similar results in Earth or Mars conditions, can predict very different circulation patterns in Venus-like conditions.…”

Angular momentum conservation in a simplified Venus General Circulation Model

“…We integrate the FMS Venus GCM from rest for 300 years (%70,000 Earth days) in the configuration described in Lee and Richardson (2010). In this experiment the GCM uses a spectral element dynamical-core model with a triangular truncation at wavenumber 21 (T21).…”

“…Both suggested that the simplified forcing alone was insufficient to produce a realistic atmospheric state with their GCMs. We have shown in an integration of the simplified FMS Venus GCM (Lee and Richardson, 2010) that angular momentum is conserved to a rate of better than 2% per 1000 years, with 98% of the angular momentum being directly attributable to the torques applied through the lower boundary layer. The longest integrations used in recent publications are the multi-century integrations in Lebonnois et al (2011) (the ''ISSI inter-comparison''), too short for numerical non-conservation to have a significant impact in the FMS Venus GCM.…”

“…To examine AM conservation in the FMS Venus GCM we used the simplest possible experiment configuration (Lee et al, 2005(Lee et al, , 2007Lee and Richardson, 2010). This configuration is the same as that used by other groups (e.g.…”

On the small-scale turbulence parameters in the atmosphere of venus and their use in the global circulation models

“…In currently available models, the small scale tur bulence is accounted for, very roughly, by the semiem pirical theories (Yamamoto and Takahashi, 2003;2007;Hollingsworth, Young, and Schubert, 2007;Lebonnois et al, 2010;Lee, Lewis, and Read, 2007;Lee and Richardson, 2010;Parish, Schubert, and Curtis, 2011) rather than by the experimental data. The experimental and theoretic profiles of zonal wind U(z) substantially differ (Counselman et al, 1980;Kerzhanovich and Limaye, 1985).…”