ON THE PHENOMENON OF NUCLEI ENHANCEMENT DURING THE EVAPORATIVE STAGE OF A CLOUD

The number of nuclei observed just after a cloud evaporates is classic ally equal to the sum of the number of interstitial nuclei plus the dr oplet number density. There are occasional reports of more nuclei prod uced in the vicinity of evaporating cloud droplets than the classical amount. The purpose of our paper is to provide an overview of the phen omenon of nonclassical nuclei production, with the ultimate purpose of laying the foundation for future efforts designed to formalize the me chanism that explains this phenomenon. The available literature is dis cussed in conjunction with field and laboratory measurements and sugge sts that a nonclassical generation of particles depends on the (i) rel ative humidity of the air surrounding the droplets, RH, and (ii) the p hysical and chemical characteristics of the evaporating clouds. implic it within the available literature is the importance of the temporal a nd spatial resolution of sampling during the final stage of a cloud cy cle and shortly thereafter. A possible explanatory mechanism is presen ted and is 'naturally' preliminary. (C) 1998 Elsevier Science B.V. All rights reserved.