Dynamics of the Atmospheres of Giant Planets Inside and Outside the Solar System

Adam Showman
University of Arizona, Lunar and Planetary Labs

April 28, 2008, 4PM, LPL 308

Here I discuss the atmospheric circulation 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. East-west jet streams dominate the atmospheric circulation of our local giant planets. The question of what causes these jets has remained a puzzle since high-resolution spacecraft images of these planets were returned in the 1970s and 1980s. Moreover, the equatorial jet is eastward (superrotating) on Jupiter and Saturn but westward (subrotating) on Uranus and Neptune, which has proven difficult to explain within the context of a single model. Here, I present numerical simulations to test the hypothesis, repeatedly suggested in the literature, that moist convection and other "weather layer" processes can produce the jet patterns observed on these planets, including the equatorial jet direction. The simulations exhibit the development of numerous jet streams, including equatorial superrotation for the Jupiter-like cases and equatorial subrotation for the Uranus/Neptune-like cases. While our model contains many simplifications and is not necessarily unique, the approximate agreement with the observed wind profiles supports the idea that moist convection plays an important role in generating the jets on giant planets. I then move 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 lightcurves, spectra, albedo, and atmospheric composition. Recent observations place constraints on the day-night temperature differences and atmospheric circulation patterns of several hot Jupiters. I will describe theoretical ideas and numerical simulations of the atmospheric circulation of these planets with the goal of explaining existing observations and shedding light on the exotic meteorology of these planets.


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