This week from AGU: Supperrotation on Venus and Titan, exploratory modeling

Planetary scientists are still puzzling over how superrotation—when a planet's atmosphere rotates faster than its surface—develops on a small or slowly rotating planet like Venus or Titan. Previous researchers have suggested that a certain kind of atmospheric eddy activity is required to retain the momentum surplus over the equator of a planet, where superrotation develops, but have not yet identified this underlying mechanism.

Wang and Mitchell set out to investigate the development of superrotation by examining the spontaneously generated wave activities using a global atmospheric simulation with different physical parameter settings. The authors find that a global instability that couples the equatorial Kelvin wave, an equatorially trapped gravity wave, and the midlatitude Rossby wave, a wave that emerges due to the variation of the Coriolis effect or the wind velocity gradient, could be the underlying mechanism supporting the zonal momentum transport toward the equator.

The authors note that their findings could help pinpoint parameters that if present could predict the occurrence of superrotation on certain planets. Knowing this would help scientists and engineers design spacecraft and landing missions that are better able to survey specific targets in a planet's atmosphere and on its surface.

Scientists know well that correlation is not causation, but exploratory modeling provides a way to identify causality within complex systems.

Source: American Geophysical Union