Buoyancy perturbation
= Buoyancy perturbation
{title2=$b'$}
A <buoyancy perturbation> is the departure $b'$ from a prescribed basic buoyancy field. In a <fluid> with constant <buoyancy frequency> $N$, <vertical velocity> $w'$ changes it according to $(\partial_t+\mathbf U\cdot\nabla)b'=-N^2w'$.