Simple Solutions to Equilibrium Cumulus Regimes in the Convective Boundary Layer

Mixed Layer Models have been very successful in describing the evolution of the turbulent atmospheric boundary layer, yet this is often confined to homogeneous (i.e. cloudless or stratocumulus-capped) boundary layers. We have developed a modelling framework which extends the mixed layer model to cumulus convection, while retaining the characteristic simplicity of the mixed layer model.

The presented framework allows for the evaluation of equilibrium states on the basis of the current environmental conditions. This equilibrium state is largely independent of the initial conditions, and therefore presents an asymptotic tendency which might help deepen our understanding of the boundary layer dynamics. Using the profile of the buoyancy flux, cloudless, coupled and decoupled regimes can be distinguished a priori. These predictions are tested by comparison to a large number of independent Large-Eddy Simulations, and are found to be in good agreement with the simulation results.