The Transition to Superrotation in Terrestrial Atmospheres

Abstract

We show that by changing a single non-dimensional number, the thermal Rossby number, global atmospheric simulations with only axisymmetric forcing pass from an Earth-like atmosphere to a superrotating atmosphere that more resembles the atmospheres of Venus or Titan. The transition to superrotation occurs under conditions in which equatorward-propagating Rossby waves generated by baroclinic instability at intermediate and high latitudes are suppressed, which will occur when the deformation radius exceeds the planetary radius. At large thermal Rossby numbers following an initial, nearly axisymmetric phase, a global baroclinic wave of zonal wavenumber one generated by mixed barotropic-baroclinic instability dominates the eddy flux of zonal momentum. The global wave converges eastward zonal momentum to the equator and deposits westward momentum at intermediate latitudes during spinup and before superrotation emerges, and the baroclinic instability ceases once superrotation is established. A global barotropic mode of zonal wavenumber one generated by a mix of high- and low-latitude barotropic instability is responsible for maintaining superrotation in the statistically steady state. At intermediate thermal Rossby numbers, momentum flux by the global baroclinic mode is subdominant relative to smaller baroclinic modes, and thus strong superrotation does not develop.

accepted for publication in JGR-Planets

Cited by in corpus (22)

• Equatorial superrotation on tidally locked exoplanets
• Atmospheric dynamics of terrestrial exoplanets over a wide range of orbital and atmospheric parameters
• Deciphering thermal phase curves of dry, tidally locked terrestrial planets
• Climate instability on tidally locked exoplanets
• Atmospheric convection plays a key role in the climate of tidally-locked terrestrial exoplanets: insights from high-resolution simulations
• Exploring the Venus global super-rotation using a comprehensive General Circulation Model
• Comparative terrestrial atmospheric circulation regimes in simplified global circulation models: I. from cyclostrophic super-rotation to geostrophic turbulence
• Hot Jupiter Diversity and the Onset of TiO/VO Revealed by a Large Grid of Non-Grey Global Circulation Models
• Atmospheric bistability and abrupt transitions to superrotation: wave-jet resonance and Hadley cell feedbacks
• Axisymmetric constraints on cross-equatorial Hadley cell extent
• Nonequilibrium thermodynamics of circulation regimes in optically-thin, dry atmospheres
• Atmospheric circulation, chemistry, and infrared spectra of Titan-like exoplanets around different stellar types
• Atmospheric dynamics of temperate sub-Neptunes. Part I: dry dynamics
• Atmospheric dynamics on terrestrial planets with eccentric orbits
• Comparative terrestrial atmospheric circulation regimes in simplified global circulation models: II. energy budgets and spectral transfers
• Equatorial superrotation in Held & Suarez-like flows with weak equator-to-pole surface temperature gradient
• The dependence of global super-rotation on planetary rotation rate
• Oceanic Superrotation on Tidally Locked Planets
• Zonal-mean atmospheric dynamics of slowly-rotating terrestrial planets
• General Circulation Model Errors are Variable across Exoclimate Parameter Spaces
• Mechanisms of Superrotation in Slowly-Rotating and Tidally-Locked Planets
• Superrotation of Titan's stratosphere driven by the radiative heating of the haze layer