The effect of CCN regeneration on the evolution of stratocumulus cloud layers

Abstract

The paper presents the results from a numerical simulation of a stratocumulus cloud-topped boundary layer (CTBL) based on a newly developed model that includes 3-D LES dynamical framework and explicit formulation of cloud microphysics. The presented results reveal such interesting features of CTBL evolution as decoupling of the stratiform cloud layer and formation of bimodal spectra due to the processes of droplet evaporation and reactivation. The effect of CCN regeneration on cloud properties has been studied in a set of four experiments. It is shown that the process of CCN regeneration may be quite important in formation and evolution of cloud microphysical and radiative properties, while cloud dynamical structure appears to be less affected. We also conclude that the parameters of stratocumulus cloud are rather insensitive to the exact form of CCN spectrum regenerated after droplet evaporation. The conclusion may be of significance in prioritizing the processes for explicit cloud modeling. © 1994.