The puzzling Venusian polar atmospheric structure reproduced by a general circulation model

• Published in: Nature communications Vol. 7; no. 1; p. 10398
• Main Authors: Ando, Hiroki, Sugimoto, Norihiko, Takagi, Masahiro, Kashimura, Hiroki, Imamura, Takeshi, Matsuda, Yoshihisa
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.02.2016; Nature Publishing Group; Nature Portfolio
• Subjects: 704/106/35; 704/445/823; Atmosphere; Cold; General circulation models; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary); Venus; Vortices; Japan
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms10398

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. Unlike some planets, the Venusian polar vortex is warmer than the mid-latitudes at cloud-top level, but the mechanism behind this is unknown. Here, the authors use a general circulation model and suggest the cold collar and warm polar regions are due to residual mean meridional circulation intensified by thermal tides.