Earth Planets Space, Vol. 61 (No. 10), pp. e45-e48, 2009E-LETTER
Masaru Yamamoto1 and Masaaki Takahashi2
1Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-Kouen, Kasuga 816-8580, Japan
2Center for Climate System Research, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8568, Japan
(Received August 11, 2009; Revised October 20, 2009; Accepted October 24, 2009; Online published November 16, 2009)
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.
Key words: Venus, topography, general circulation, superrotation, orographically-forced wave.