Imaginary part of the surface pressure variation created by the semidiurnal thermal tide as a function of the normalized tidal frequency for a Venus-sized planet of surface pressure p_s = 10 bar and orbital radius a = a_Venus. Results obtained using GCM simulations are designated by points. Spectra are plotted for two cases: the reference case of the study, where the atmosphere is mainly composed of N₂ (black line), and the case treated in Appendix C, where the atmosphere is composed of CO₂ with a mixture of water vapour and sulphuric acid.