1993 Volume 71 Issue 4 Pages 503-515
To understand various development mechanisms of disturbances in the Eady problem, the quasigeostrophic equation system is extended to include the horizontal boundary conditions. First, we distinguish continuous-spectrum waves from the modal waves by using potential vorticity. Next, we derive the "wave momentum" and clarify its relationship with the Eliassen-Palm flux. Finally, the necessary condition for the development of waves in the baroclinic flow is expressed by evaluating the EP-flux divergence. In Farrell (1984) or Thorncroft and Hoskins (1990), shallow vortices develop algebraically, as the result of wave-wave interaction of a boundary modal wave and internal continuous-spectrum waves. These interactions are clearly indicated by the EP-flux convergence around the critical level.