From cloud condensation nuclei to cloud droplets: a turbulent model

摘要

The formation of a warm vertical cloud is classically described by the evolution of microscopic droplets [1]. Droplets start to nucleate around solid particles in a favourable environment (i.e. for positive supersaturation in the absence of solute effect). Then, if the available vapour is sufficient, they grow by condensation. Once their size is large enough, their terminal velocity is no more negligible and they start to collide with both slower and faster droplets. The resulting growth by coalescence is explosive and eventually a precipitation can occur. This simple description is able to capture the basic mechanisms behind the first development of the cloud.