EFFECTS OF RADIATIVE DAMPING ON RESONANTLY GENERATED INTERNAL GRAVITY-WAVES

Internal gravity waves can propagate indefinitely upwards when a fluid is continuously stratified and unbounded vertically. This causes radiative damping of waves which are resonantly generated by the interaction between a mean flow and a topographic feature at the lower boundary. An evolution equation of Benjamin-Davis-Acrivos type, including temporal evolution, detuning, nonlinearity, dispersion, radiative damping, and forcing, is derived to describe the wave behavior. Using a pseudospectral method, we obtain and discuss various numerical results, especially for the resonant cases, covering forcing whose polarity is the same as, or opposite to, that of a free solitary wave, and for weak or strong radiative damping. In practice, weak-radiative cases are likely to be realized when an inversion layer exists at a certain low level over a mountain range.