Pierrehumbert, R. T., 1985: Notes and Correspondence: Stratified semigeostrophic flow over two-dimensional topography in an unbounded atmosphere. Journal of the Atmospheric Sciences, 42 (5), 523-526.

Abstract: We obtain simple closed-form expressions describing stratified, rotating flow over an infinite ridge in the semigeostrophic regime. The results are used to discuss the degree to which air parcels slow down as they approach a steep mountain. The critical Burger number for the appearance of infinite velocities at the mountain crest is calculated for several mountain profiles. It is shown that for Gaussian and bell-shaped mountains the breakdown occurs in a range in which the upstream deceleration is not pronounced.