Natural convection

Convection driven primarily by buoyancy generated by heating or cooling, rather than an externally imposed mean flow. In a constant-flux unstable surface layer, the local speed scales as $(B_{0}z{)}^{1/3}$.

For a positive approximately constant vertical turbulent buoyancy flux, dimensional turnover scaling gives $K_b\sim B_0^{1/3}{z}^{4/3}$ and $N^2\sim -B_0^{2/3}{z}^{-4/3}$. The negative squared frequency describes unstable overturning, not a real restoring oscillation. The leading dissipation is height-independent, unlike neutral wall turbulence.