The air flow over a ridge — the effects of the upper boundary and high‐level conditions

The solution obtained by perturbation theory for the airflow over a ridge depends on the mathematical conditions imposed at the upper boundary of the region for which a solution is obtained. New arguments are developed as to the choice of upper‐boundary condition appropriate to the atmospheric problem; these lead to the solution already adopted by Queney (1947). In certain airstreams it is possible for lee waves to have their largest amplitude in the upper troposphere and stratosphere. The character of the airstream at high levels plays a dominant part in determining the characteristics of these waves, but it has only negligible effects on the more familiar type of lee wave which has its largest amplitude in the lower troposphere.