  In this paper, the properties of stably stratified turbulence (SST) and
turbulent thermal convection are contrasted. A key difference between these
flows is the sign of the kinetic energy feed by buoyancy, $\mathcal{F}_B$. For
SST, $\mathcal{F}_B < 0$ due to its stable nature; consequently, the kinetic
energy flux $\Pi_u(k)$ decreases with wavenumber $k$ that leads to a steep
kinetic energy spectrum, $E_u(k) \sim k^{-11/5}$. Turbulent convection is
unstable, hence $\mathcal{F}_B > 0$ that leads to an increase of $\Pi_u(k)$
with $k$; this increase however is marginal due to relatively weak buoyancy,
hence $E_u(k) \sim k^{-5/3}$, similar to that in hydrodynamic turbulence. This
paper also describes the conserved fluxes for the above systems.
