When the ridge is 500 m high, the pressure drag maximizes at 6.5 days, two days after frontal passage and then decreases rapidly. In contrast, when the ridge is 2 km high, the drag maximizes slightly earlier (at 6 days) and remains large until the simulation terminates at 7.5 days. In both cases, the vertical momentum fluxes slightly above mountain-top level are significantly less than the pressure drag. The difference between the pressure drag and the vertical momentum flux in the momentum budget is primarily balanced by the Coriolis force acting on the ageostrophic wind.
The 2-km high mountain produces extensive wave breaking, primarily (1) at low levels in the lee of the terrain prior to frontal passage and (2) in the stratosphere after frontal passage. This wave breaking causes significant removal of the cross-mountain momentum at both of these levels, a significant fraction of which, is focused in distinct large-scale structures well downstream of the topography.