A zonally averaged, quasi-geostrophic residual Eulerian model is used to illustrate how the adjustment of the middle atmophere to externally imposed forcing depends on internal dissipative properties (parameterized as Newtonian cooling a and Rayleigh friction KR) and on the periodicity of the forcing. It is shown that when the problem is formulated in this manner, many well-known properties of the stratosphere/mesosphere system (e.g., the relative efficiency of wave versus diabatic driving of the meridional circulation, and the near radiative equilibrium of much of the stratosphere) are succinctly expressed in terms of the governing elliptic differential equation and its solutions. Despite its simplicity, the model is a useful heuristic tool for studying the response of the middle atmosphere to external forcing. Abstract A zonally averaged, quasi-geostrophic residual Eulerian model is used to illustrate how the adjustment of the middle atmophere to externally imposed forcing depends on internal dissipative properties (parameterized as Newtonian cooling a and Rayleigh friction KR) and on the periodicity of the forcing. It is shown that when the problem is formulated in this manner, many well-known properties of the stratosphere/mesosphere system (e.g., the relative efficiency of wave versus diabatic driving of the meridional circulation, and the near radiative equilibrium of much of the stratosphere) are succinctly expressed in terms of the governing elliptic differential equation and its solutions. Despite its simplicity, the model is a useful heuristic tool for studying the response of the middle atmosphere to external forcing.