Scientific Colloquium
February 16, 2007
"Dynamics of the Atmospheres of Giant Planets Inside and Outside the Solar System"

Here I discuss the atmospheric circulations on the giant planets in our solar system -- Jupiter, Saturn, Uranus, and Neptune -- as well as on some of the 200-odd giant planets discovered around other stars.  The atmospheric circulations of our local giant planets are characterized by banded cloud patterns, numerous east-west jet streams, and stable vortices at the cloud level.  The question of what causes these features has remained a puzzle since high-resolution spacecraft images of these planets were returned in the 1970s and 1980s.  A probable hypothesis is that turbulence injected into the cloud layer reorganizes into zonal jets and large vortices.  However, existing models have been insufficient to test the hypothesis.  Here, I describe basic dynamical ideas and numerical simulations to investigate whether this process can produce Jupiter-like jets, and, if so, whether such jets penetrate deeply into the interior or remain confined to the forcing layer. The simulations show development of vortices and jets that resemble the giant planets in broad outline.  But the details -- such as whether jets dominate over vortices, whether the jets penetrate deeply into the interior or remain confined to the forcing level, and whether the jet pattern (if any) resembles Jupiter and Saturn -- depends on the type of forcing, the vertical temperature structure, and other parameters.  I then extend these ideas to extrasolar planets, focusing on those planets orbiting very close to their stars -- the so-called "hot Jupiters." These planets are intensely heated on their daysides and are expected to have a vigorous circulation that shapes the day-night temperature difference, infrared lightcurve, spectra, albedo, and atmospheric composition.  Recent observations place constraints on the wind speeds, day-night temperature difference, and albedos of several hot Jupiters.  I will describe theoretical ideas and numerical simulations of the atmospheric circulation of these planets with the goal of interpreting these and future observations of these planets.

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