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We present global, three-dimensional numerical simulations of the atmosphericcirculation on HD 209458b and HD 189733b and calculate the infrared spectra andlight curves predicted by these simulations, which we compare with availableobservations. Radiative heating/cooling is parameterized with a simplifiedNewtonian relaxation scheme. Our simulations develop day-night temperaturecontrasts that vary strongly with pressure. At low pressure (<10 mbar), airflows from the substellar point toward the antistellar point, both along theequator and over the poles. At deeper levels, the flow develops an eastwardequatorial jet with speeds of 3-4 km/sec, with weaker westward flows at highlatitudes. This basic flow pattern is robust to variations in model resolution,gravity, radiative time constant, and initial temperature structure. Nightsidespectra show deep absorption bands of H2O, CO, and/or CH4, whereas on thedayside these absorption bands flatten out or even flip into emission. Thisresults from the strong effect of dynamics on the vertical temperature-pressurestructure; the temperature decreases strongly with altitude on the nightsidebut becomes almost isothermal on the dayside. In Spitzer bandpasses, ourpredicted planet-to-star flux ratios vary by a factor of 2-10 with orbitalphase, depending on the wavelength and chemistry. For HD 189733b, where adetailed 8-micron light curve has been obtained, we correctly produce theobserved phase offset of the flux maximum, but we do not explain the fluxminimum and we overpredict the total flux variation. This discrepancy likelyresults from the simplifications inherent in the Newtonian relaxation schemeand provides motivation for incorporating realistic radiative transfer infuture studies.

Atmospheric Circulation of Hot Jupiters: Three-dimensional circulation models of HD 209458b and HD 189733b with Simplified Forcing