On the efficiency of nucleation scavenging

Abstract

The activation process near cloud base for submicrometer, soluble atmospheric aerosols is described and special attention is focused on the fraction, Ԑ, of the total aerosol mass concentration that form cloud droplets. The variation of Ԑ with updraft speed for various aerosol size distributions is calculated by means of an adiabatic, one-dimensional Lagrangian cloud model. Calculations are made for aerosol particles consisting of pure ammonium bisulphate, (NH₄)HSO₄ and the results show that for a clean continental background aerosol population. Ԑ should be very near unity for all updraft speeds. For an average urban aerosol population, Ԑ is close to unity for convective clouds. but for stratiform cases Ԑ decreases rapidly as the updraft velocity is lowered. DOI: 10.1111/j.1600-0889.1984.tb00255.x