Turning height of a stationary wave in linear shear
= Turning height of a stationary wave in linear shear
{title2=$z_t=(N/k-U_0)/S$}
For constant <buoyancy frequency> $N$ and $U=U_0+Sz$ with $S>0$, a stationary component of horizontal <wavenumber> $k$ turns at $z_t=(N/k-U_0)/S$ if it propagates at the source. Its vertical <wavenumber> vanishes there; <WKB approximation> fails and an <Airy function> transition connects reflection to an upper <evanescent wave>.