On the role of drizzle in stratocumulus and its implications for large-eddy simulation

Large-eddy simulation (LES) of marine stratocumulus cloud-topped boundary layers show a surprisingly large sensitivity to the prescribed forcing-this being at odds with the widespread and persistent occurrence of this cloud type. However, most LES studies have not taken drizzle explicitly into account. This note explores the damping effect (i.e. reducing the sensitivity to the forcing) that drizzle might have on the stratocumulus cloud-topped boundary layer. A single-column model is used to illustrate the difference in response in one model version with drizzle taken into account and one in which drizzle is inactivated. Results are shown for a simulation of the diurnal cycle of stratocumulus clouds over sea; they support the notion that the impact of drizzle is underrated in the present-day modelling of stratocumulus-topped boundary layers.