Gravity waves (GWs) and solar tides (STs) are main constituents of the dynamical coupling between the atmospheric layers. To the largest part they are generated in the lower atmosphere. STs are large-scale waves that modulate all dynamical fields in the mesosphere and thus leave a strong imprint on the dynamics of the latter. Predominantly via momentum deposition GWs to a large extent control the mesospheric mean circulation. GWs and STs interact strongly with each other: STs modulate the propagation of GWs, while the momentum deposition by breaking GWs influences the amplitude and phase structure of STs in the mesosphere. So far general circulation models (GCMs) have described this interaction process with insufficient accuracy. Conventional GW parameterizations, although indispensable for capturing the effect of mesoscale GWs, neglect both the impact of the transience of the ST fields and that of horizontal gradients in the large-scale wind fields in the atmosphere. Recent work has investigated the GW-ST interaction in a coupled model for linear STs and nonlinear GWs, the latter described using fully interactive ray tracing. Corresponding results will be presented, showing the importance of wave transience and lateral propagation.