Mesoscale variability of turbulence-generating mechanisms in southeast-Pacific stratocumulus

Boundary layer cloud systems over the southeast Pacific are frequently characterized by cells of precipitation associated with strong updraft/downdraft couplets that are embedded in broad regions of stratocumulus. Cloud-top radiative cooling is the predominant mechanism for generating turbulent kinetic energy (TKE) in the stratocumulus regions. Positive vertical velocity skewness in the precipitation cells, on the other hand, implies a circulation rooted in the subcloud layer and largely independent of cloud-top cooling mechanisms. A series of numerical simulations serve to isolate the relative importance of cloud top radiative cooling (top–down) and surface-driven (bottom–up) buoyancy mechanisms in establishing the mesoscale structure of cloud and turbulence properties.