Peter D. Killworth and Jeffrey R. Blundell
Southampton Oceanography Centre, Empress Dock, Southampton SO14 3ZH, U.K.
The one-dimensional examples of the dispersion relation for planetary waves under the WKBJ assumption given in Killworth and Blundell (2004) are extended to two dimensions, and analysed globally. The dispersion relations are complicated, and there is a nontrivial lower bound to the frequency, given by the column maximum of what would be the local Doppler shift to the frequency. This generates short waves of a much higher frequency than would be expected from traditional theory; these waves can have larger phase velocities than long waves, but do not appear to have faster group velocities. The longer waves possess phase speeds in excellent agreement with recent remotely sensed data. Waves cannot propagate efficiently across ocean basins, suggesting that mechanisms other than eastern boundary generation may be playing a role in the ubiquitous nature of planetary waves.