The effects of rotation on flow of a single layer over a ridge

The effects of the Coriolis force on the hydrostatic flow of a single lower layer over a two‐dimensional ridge are described. For short periods the flows resemble those of the non‐rotating case, but after a few hours (in the atmospheric context) effects of rotation become significant. For steady‐state flow over ridges and plateaux, critical conditions near the crest of the obstacle can control the flow in the same manner as for conventional hydraulics. However, steady disturbances are only manifested a finite distance upstream. For initial Froude number F o < 1, upstream disturbances decay on the length scale (1 – F ) 1/2 L , where L is the Rossby deformation radius. For F o > 1, upstream bores (where they exist) become arrested at a finite distance ahead of the barrier. When flow on the lee side is supercritical, steady lee‐side disturbances consist of nonlinear inertial oscillations. Obstacle shape is important in determining upstream and downstream flow. The results are useful for understanding atmospheric flows over mesoscale ridges.