Revisiting Queney's Flow over a Mesoscale Ridge

The foundations for our understanding of wave generation by topography were established in studies of Queney (1947,1948) for steady flow past a two-dimensional ridge. In this seminal work, the downstream radiation pattern was inferred from the dispersion characteristics of linear gravity waves. Queney's streamline figures, obtained by approximating a Fourier integral, are frequently reproduced as the canonical illustration of downstream topographic waves. For the case of constant stratification with f-plane rotation, we find there are significant differences in the near-ridge flow pattern upon comparing the original approximation (Queney 1948, Figure 3) with direct computation of the Fourier integral. Flow corrections in the near-field aloft and downslope regions will be presented in updated figures. These new figures are computed using a high-order numerical integration scheme which is especially designed to resolve the near-inertial singular waves. The implementation of these ideas to computing three-dimensional topographic wave flows will be discussed. Finally, a new analytical approximation suggests that an additional by-product of the topographic wave generation is a weak, near-inertial wave that is produced by backscattering from the downslope surface.