Internal-wave slope criticality
= Internal-wave slope criticality
Let an <internal gravity wave> energy ray make angle $\theta$ with the horizontal, so that $\sin\theta=\omega/N$. A boundary of local slope magnitude $s$ is subcritical, critical, or supercritical according as $s$ is smaller than, equal to, or larger than $\tan\theta$. At criticality the inviscid reflected wavelength tends to zero.