  We present global, three-dimensional numerical simulations of the atmospheric
circulation on HD 209458b and HD 189733b and calculate the infrared spectra and
light curves predicted by these simulations, which we compare with available
observations. Radiative heating/cooling is parameterized with a simplified
Newtonian relaxation scheme. Our simulations develop day-night temperature
contrasts that vary strongly with pressure. At low pressure (<10 mbar), air
flows from the substellar point toward the antistellar point, both along the
equator and over the poles. At deeper levels, the flow develops an eastward
equatorial jet with speeds of 3-4 km/sec, with weaker westward flows at high
latitudes. This basic flow pattern is robust to variations in model resolution,
gravity, radiative time constant, and initial temperature structure. Nightside
spectra show deep absorption bands of H2O, CO, and/or CH4, whereas on the
dayside these absorption bands flatten out or even flip into emission. This
results from the strong effect of dynamics on the vertical temperature-pressure
structure; the temperature decreases strongly with altitude on the nightside
but becomes almost isothermal on the dayside. In Spitzer bandpasses, our
predicted planet-to-star flux ratios vary by a factor of 2-10 with orbital
phase, depending on the wavelength and chemistry. For HD 189733b, where a
detailed 8-micron light curve has been obtained, we correctly produce the
observed phase offset of the flux maximum, but we do not explain the flux
minimum and we overpredict the total flux variation. This discrepancy likely
results from the simplifications inherent in the Newtonian relaxation scheme
and provides motivation for incorporating realistic radiative transfer in
future studies.
