Adiabatic Cloud Droplet Activation and Growth

Width of the droplet spectrum is an important parameter affecting cloud radiative properties as well as drizzle and rain development in warm ice-free clouds. We consider formation and growth of cloud droplets in an air parcel rising across the subcloud layer, reaching the cloud base, and continuing its rise carrying cloud droplets continuously growing by condensation of water vapor. We focus on the evolution of the spectral width. We show that the simplified droplet growth equation often applied in cloud simulations is not accurate enough to faithfully predict width of the droplet spectrum aloft, especially in polluted weak-updraft shallow clouds such as a continental stratocumulus.