Technical note: Parameterising cloud base updraft velocity of marine stratocumuli

Abstract. The number of cloud droplets formed at the base depends on both properties aerosol particles and updraft velocity an air parcel base. As spatial scale updrafts is too small to be resolved in global atmospheric models, commonly parameterised based available turbulent kinetic energy. Here we present alternative methods through parameterising high-resolution large-eddy simulation (LES) runs case marine stratocumulus clouds. First use our simulations assess accuracy a simple linear parameterisation where only top radiative cooling. In addition, two different machine learning (Gaussian process emulation random forest) that account for boundary layer conditions properties. We conclude parameterisations reproduce LES-based velocities about same accuracy, while approach employing cooling produces average lower coefficient determination higher root mean square error values. Finally, apply these find key parameters affecting velocities.