= Turning level of a stationary internal wave
{title2=$m^2(z_t)=0$}
A vertically propagating <stationary topographic internal gravity wave> meets a turning level when its squared vertical <wavenumber> changes from positive to negative. The <stationary internal-wave WKB solution> then fails locally. A simple zero is resolved by an <Airy function> transition connecting incident and reflected waves below to a decaying <evanescent wave> above. For negligible wind curvature the condition is $|kU(z_t)|=N(z_t)$, distinct from the zero-intrinsic-frequency <critical layer in a shear flow>.
Back to article page
