title: The puzzling Venusian polar atmospheric structure reproduced by a general circulation model.
abstract: Unlike the polar vortices observed in the Earth, Mars and Titan atmospheres, the observed Venus polar vortex is warmer than the midlatitudes at cloud-top levels (∼65 km). This warm polar vortex is zonally surrounded by a cold latitude band located at ∼60° latitude, which is a unique feature called 'cold collar' in the Venus atmosphere. Although these structures have been observed in numerous previous observations, the formation mechanism is still unknown. Here we perform numerical simulations of the Venus atmospheric circulation using a general circulation model, and succeed in reproducing these puzzling features in close agreement with the observations. The cold collar and warm polar region are attributed to the residual mean meridional circulation enhanced by the thermal tide. The present results strongly suggest that the thermal tide is crucial for the structure of the Venus upper polar atmosphere at and above cloud levels.
authors.affiliation: Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Kanagawa 252-0222, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Ando
authors.affiliation: Research and Education Center for Natural Sciences, Department of Physics, Keio University, Yokohama, Kanagawa 223-8521, Japan.
authors.forename: Norihiko
authors.initials: N
authors.lastname: Sugimoto
authors.affiliation: Faculty of Science, Kyoto Sangyo University, Kita-ku, Kyoto 603-8555, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Takagi
authors.affiliation: Japan Agency for Marine-Earth Science and Technology, Yokohama, Kanagawa 236-0001, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kashimura
authors.affiliation: Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Kanagawa 252-0222, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Imamura
authors.affiliation: Department of Astronomy and Earth Sciences, Tokyo Gakugei University, Koganei, Tokyo 184-8501, Japan.
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Matsuda
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