This thesis contributes to the discussion, how the large-scale and mesoscale atmospheric motions interact and how the vertical coupling of the atmosphere is influenced by mesoscale waves. The results from our mechanistic GCM are twofold. Firstly, the mesoscale upper tropospheric kinetic energy spectrum can be explained by stratified turbulence. Secondly, the mesoscale energy deposition in the upper mesosphere can be explained by the vertical pressure flux carried by mesoscale gravity waves from the troposphere, which is converted into kinetic energy of these waves and then dissipated.