On the scale analysis of traveling planetary waves

In a well-known study, BURUER (1958) analyzed the importance of the major terms in the vorticity equation, with particular attention to the planetary waves of greatest scale. He concluded that the vorticity equation becomes simply a “balance equation” equivalent to the geostrophic approximation for the largest-scale waves. The purpose of this note is to show that the vorticity equation does retain some useful predictive and diagnostic properties when applied to planetary waves.