Two 60-day simulations of the global atmospheric circulation produced by the Canadian Climate Centre general circulation model were analyzed to determine the solar diurnal and semidiurnal variations in the wind, pressure, and precipitation fields. In these simulations the radiative transfer calculations were performed every hour in order to resolve adequately the diurnal cycle. One simulation was for boreal summer, and the other was for winter conditions. The diurnal and semidiurnal surface pressure variations in the model were found to be quite realistic, although somewhat smaller than actually observed. Even some fairly subtle details of the geographical and seasonal variability of the solar tidal pressure oscillation were well simulated. The daily cycle of the wind in the model also appears to be reasonably consistent with the limited observations available. By contrast, the diurnal and semidiurnal variations of precipitation were not successfully simulated by the model. Linear tidal theory calculations were performed with thermal forcings, vertical resolution, and boundary conditions similar to those in the full general circulation model. These calculations allowed an evaluation of the effects of the different numerical approximations in the general circulation model on the simulated tide. One striking result of these linear computations was the indication of a tendency for the effects of the ''rigid-lid'' upper boundary condition to compensate for the omission of the thermal tidal forcing above the top level of the model.