Abstract
The behavior of very long waves in a two-parameter model with no divergence in the mean flow has been investigated. It is found that the temperature field and the pressure field move almost independently of each other. The pressure field will retrograde with a speed comparable to the Rossby speed for non-divergent waves, while the temperature field progresses slowly. As a result, the latter field will precede the pressure field after a while, verifying an earlier observation in these forecasts. Introducing a divergence in the vertical mean flow not only greatly reduces the retrogression, but a stronger coupling then exists between the temperature and pressure fields.
