  We developed a time-dependent radiative model for the atmosphere of HD209458b
to investigate its thermal structure and chemical composition. Time-dependent
temperature profiles were calculated, using a uniform zonal wind modelled as a
solid body rotation. We predict day/night temperature variations of 600K around
0.1 bar, for a 1 km/s wind velocity, in good agreement with the predictions by
Showman & Guillot (2002). On the night side, the low temperature allows the
sodium to condense. Depletion of sodium in the morning limb may explain the
lower than expected abundance found by Charbonneau et al (2002).
