J. Lett . Controls what we observe. To conserve mass as it enters lower density layers, ascending fluid diverges and turns over into a downflow in approximately a scale height.
Convective flow is like a fountain.
It is consists of warm, broad, fairly laminar, slow upflows, surrounded by cool, narrow, turbulent, fast downdrafts. The horizontal size of the upflow cells decreases as the as the scale height decreases approaching the surface. Only a small fraction of ascending fluid actually reaches the surface. The top surface shows the emergent intensity. The interior colors show the temperature and the arrows show the flow velocity.