The source supplies the kinematic buoyancy flux . The unstratified line plume velocity scale is . Comparing this with the stratification time scale gives the stratified line-plume height scale
If , the initial plume is only weakly affected by the stable density stratification and reaches the ceiling much like an unstratified wall plume. If , its buoyancy flux falls substantially during the rise; it approaches neutral buoyancy near the upper room, overshoots because of its momentum flux, and spreads as a horizontal buoyant intrusion. If , the plume reaches neutral buoyancy low in the room and forms a low intrusion after a modest overshoot. In each sketch the plume widens by entrainment, while increasing lowers the neutral-buoyancy and overshoot heights.
A line plume of kinematic buoyancy flux rising through uniform buoyancy frequency has the dimensional height scale
It measures the height over which ambient stratification removes an order-one fraction of the plume buoyancy before the plume reaches neutral buoyancy and spreads as a buoyant intrusion.