What maintains the superrotation of Venus's atmosphere? · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title
What maintains the superrotation of Venus's atmosphere?
Plain
The solid body of Venus turns once every 243 Earth days, but its clouds circle the planet in about 4 days, roughly sixty times faster. Which waves and eddies keep feeding spin into the atmosphere is unresolved.
Precise · changed · core
Revision 1: At cloud-top altitude (about 70 km) zonal winds reach about $1e4\,\mathrm{cm}/\mathrm{s}$, roughly 60 times the equatorial surface rotation speed. Identify the angular-momentum balance that maintains this superrotation: thermal tides driven by solar heating of the cloud layer, the Gierasch-Rossow-Williams mechanism (mean meridional circulation plus equatorward eddy transport by planetary waves and barotropic instability), or other waves, with their contributions as a function of altitude. An answer is a quantitative angular-momentum budget, from observations or from a general circulation model, that reproduces the observed wind profile and its variability.
Revision 2: At cloud-top altitude (about 70 km) zonal winds reach about $10^{4}\,\mathrm{cm}/\mathrm{s}$, roughly 60 times the equatorial surface rotation speed. Identify the angular-momentum balance that maintains this superrotation: thermal tides driven by solar heating of the cloud layer, the Gierasch-Rossow-Williams mechanism (mean meridional circulation plus equatorward eddy transport by planetary waves and barotropic instability), or other waves, with their contributions as a function of altitude. An answer is a quantitative angular-momentum budget, from observations or from a general circulation model, that reproduces the observed wind profile and its variability.
Settled by
Cloud-tracked and radio-occultation wind and temperature fields that resolve tidal and eddy momentum fluxes at several altitudes, matched by a general circulation model.
Kind
phenomenon
Answer type
mechanism
References
(empty)
Literature status
partially-resolved
Status note
Akatsuki cloud tracking (Horinouchi and coauthors, Science 2020, https://doi.org/10.1126/science.aaz4439) found thermal tides accelerate the equatorial cloud-top flow while waves and turbulence decelerate it; the full vertical budget remains open.
Posed since
(empty)

Decisions