Thermal Tides in the Atmosphere of Venus: Comparison of Model Results with Observations

Abstract

A linearized primitive equation (LPE) model is developed to study thermal tides in the atmosphere of Venus. The LPE model describes diurnal and semidiurnal oscillations of a cyclostrophically balanced atmosphere in which zonal velocity varies with altitude and latitude. The numerical algorithm follows Staniforth and Daley. The solar thermal forcing is increased algebraically in time to separate the forced tidal response from free atmospheric oscillations. Parameters of the basic state and forcing agree with Pioneer Venus observations. Results of the model are compared with the solar-fixed component of brightness temperature variations measured by Taylor et al. and Elson using data from the Pioneer Venus orbiter infrared radiometer (OIR). The comparison is made by convolving the computed model radiances with the weighting functions of the OIR channels. Agreement between LPE model results and OIR observations is excellent. Two interesting features of the OIR data are accounted for, namely, the slow variation of phase with altitude and the dominance of the semidiurnal oscillation over the diurnal oscillation. Success of the LPE model opens the way for calculating tidal transports of heat and momentum and assessing the role of tides in maintaining the Venus super-rotation.