Abstract
Abstract We investigate the influence of topography on Venus’ atmospheric general circulation. Based on comparative simulations with and without the Venusian topography, we elucidate the role of the topography in the fully developed superrotation. Orographically forced stationary waves are predominant over Mt. Maxwell: slightly weakening the superrotation near the cloud top. Differently from previous GCM results, the orographically forced waves do not produce significant asymmetry between the northern and southern hemispheric superrotations in the present model. Weak surface flows from mountains to lowlands are caused by the pressure dependence of the Newtonian cooling. The pattern and magnitude of the near-surface flow are largely different from those simulated in the Herrnstein and Dowling (2007) model. This implies that the parameterizations of physical processes (such as Newtonian cooling, turbulence, diffusion, and surface drag) and the model resolution could significantly influence the pattern and magnitude of the near-surface flow and the orographical forcing of planetary-scale stationary waves.
Highlights
Venus’ atmospheric environment, consisting of denseCO2, is largely different from that on the Earth, a planet which has almost the same size
Summary and Discussions The superrotation is maintained by the Gierasch mechanism under the condition that thermal and topographic forcings are given in a Venus-like General Circulation Model (GCM)
The difference between simulations with and without topography is small for the zonal mean field, though the superrotation in Exp
Summary
Venus’ atmospheric environment, consisting of denseCO2, is largely different from that on the Earth, a planet which has almost the same size. According to Yamamoto and Takahashi (2004, 2006a), thermal tides are forced by solar heating with a period of a Venusian day (117 Earth days) near the cloud top, contributing to the Gierasch mechanism through the equatorial acceleration of mean zonal flow (e.g., Newman and Leovy, 1992). We have elucidated the influences of the topography on fully developed superrotation and near-surface flow by comparing the results of our two experiments and by comparing these with recent other GCM studies (Lee, 2006; Herrnstein and Dowling, 2007).
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