Modeling stratocumulus-topped boundary-layer structure with statistical diffusion theory

Proper parameterization of vertical turbulent fluxes is of fundamental importance in numerical simulation of the atmospheric flow because surface–atmosphere exchanges are mainly associated with turbulent mixing.In this study, a parameterization for the eddy diffusivity coefficient is used in a single column model (SCM) to simulate the stratocumulus-topped boundary-layer (STBL). The scheme is suitable when a fine resolution is used in the vertical, along with a coarse resolution in the horizontal that does not allow the boundary-layer structure to be explicitly resolved (as in mesoscale and large-scale models). The parameterization is obtained by fitting turbulence data collected during the 2nd Aerosol Characterization Experiment (ACE-2). Mixing length-based analytical equations are obtained based on Taylor's statistical theory of turbulence.Single-column model simulations of two ACE-2 diurnal cases and a nocturnal ASTEX case show good agreement between model results and observations in both coupled and decoupled situations. A noticeable characteristic of the turbulence scheme, since it uses a first-order closure, is its low computational cost.