A two-level spectral model with a zonally homogeneous climate is used to study the steady response of a spherical atmosphere to tropical heating. Solutions are obtained by both averaging the time integration of the model and solving for the linear steady response.
It is found that the Rossby wave source (RWS) from a simple tropical heat source exhibits a relatively complicated horizontal structure that extends from the tropics into extratropical regions. The strong extratropical component of the RWS is important for the steady response in middle and high latitudes. A decomposition of the solution using separately the components of the RWS in tropical and extratropical regions shows that the responses to the tropical and extratropical RWSs tend to cancel in middle and high latitudes. The extratropical component of the RWS may be understood by quasigeostrophic dynamics.