J. Peralta, R. Hueso, A. Sánchez-Lavega, Y. J. Lee, A. García-Muñoz, T. Kouyama, H. Sagawa, T. M. Sato, G. Piccioni, S. Tellmann, T. Imamura, T. Satoh
(Submitted on 25 Jul 2017)
At the cloud top level of Venus (65-70 km altitude) the atmosphere rotates 60 times faster than the underlying surface, a phenomenon known as superrotation. Whereas on Venus’s dayside the cloud top motions are well determined and Venus general circulation models predict a mean zonal flow at the upper clouds similar on both day and nightside, the nightside circulation remains poorly studied except for the polar region. Here we report global measurements of the nightside circulation at the upper cloud level. We tracked individual features in thermal emission images at 3.8 and 5.0 μm obtained between 2006 and 2008 by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS-M) onboard Venus Express and in 2015 by ground-based measurements with the Medium-Resolution 0.8-5.5 Micron Spectrograph and Imager (SpeX) at the National Aeronautics and Space Administration Infrared Telescope Facility (NASA/IRTF). The zonal motions range from -110 to -60 m s−1, consistent with those found for the dayside but with larger dispersion. Slow motions (-50 to -20 m s−1) were also found and remain unexplained. In addition, abundant stationary wave patterns with zonal speeds from -10 to +10 m s−1 dominate the night upper clouds and concentrate over the regions of higher surface elevation.
Comments: 15 pages, 4 figures, 6 supplementary figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Atmospheric and Oceanic Physics (physics.ao-ph)
MSC classes: 85A20
Journal reference: Nat. Astron. 1, 0187 (2017)
DOI: 10.1038/s41550-017-0187
Cite as: arXiv:1707.07796 [astro-ph.EP] (or arXiv:1707.07796v1 [astro-ph.EP] for this version)
Submission history
From: Javier Peralta
[v1] Tue, 25 Jul 2017 02:40:44 GMT (6131kb,D)
https://arxiv.org/abs/1707.07796
