Stationary waves and slowly moving features in the night upper clouds of Venus

Abstract

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 $\mu \mathrm{m}$ 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.

15 pages, 4 figures, 6 supplementary figures

References in corpus (5)

• The Massive Star-forming Regions Omnibus X-ray Catalog
• Six years of Venus winds at the upper cloud level from UV, visible and near infrared observations from VIRTIS on Venus Express
• A chaotic long-lived vortex at Venus southern pole
• Venus cloud morphology and motions from ground-based images at the time of the Akatsuki orbit insertion
• A model of scattered thermal radiation for Venus from 3 to 5 $\mu$ m

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• A Long-lived Sharp Disruption on the Lower Clouds of Venus
• Atmospheric Dynamics of a Near Tidally Locked Earth-Size Planet
• Radiative Rayleigh-Taylor Instability and the structure of clouds in planetary atmospheres
• Global maps of Venus nightside mean infrared thermal emissions obtained by VIRTIS on Venus Express
• Characterising atmospheric gravity waves on the nightside lower clouds of Venus: a systematic analysis
• About Superrotation in Venus
• The Venus' Cloud Discontinuity in 2022
• Amateur Observers Witness the Return of Venus' Cloud Discontinuity
• Planet-wide, Concentric Density Waves in Venus's Upper Atmosphere Revealed through Polarimetry?