WMOD00300

• Title: Characterization of Silver Iodide-Sodium Iodide Ice Nuclei Using Chemical Kinetic Methodology
• Date: 5/1/1985
• State: CO
• Weather Modification - Doc Type: Report

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growth and subsequent fall velocity of oloud and preoipitation particles
to prediot the extent and location of precip1 tation reaching the ground.
Cloud partiole growth processes include growth by vapor deposition,
aocreation (Plooster and Fulcuta, 1975 and Rauber, 1'81). and aggregation
(Hobbs, et al., 1973 and Young, l'74a).
Of importanoe to the research presented in this study is the method
of initiation, or nuoleation of the ice phase in the models. Hobbs, et
ale (1973) and Rauber (1'81) arbitrarily speoified a concentration of
ice particles at a location within the cloud. Young U974a) modeled
contact and sorption ice nucleation. The contact process, collection of
aerosol particles by cloud droplets, included Brownian coagulation,
thermophoresis, and diftusiophoresis, ~dified at each time step by the
effectivity (yield) spectrum of the natural or artitic1al nuclei used.
Sorption nucleation in Young's aodel was assumed to be condensation-
freezing nucleation in the oase of natural ioe nuolei, aodified by
temperature effects on effectivity. Sorption nuoleation could also be
vapor deposition in the case of modeled AgI oloud seeding, modified by
an effeotivity spectrum dependent on supersaturation with respect to
ice. Both sorption nuoleation IlOdes were assumed to function
instantaneously in the time step. Unfortunately, in the applioation of
the model to an orographic oloud in Young U974b) only contact
nucleation was used.
Modeled ice nucleation by Plooster and Fulcuta (1'75) was similar to
Young's (1974a) sorption nuoleation, where ioe nucleation oooured
intantaneously in any time step and was controlled by the temperature
dependence of effectivity imposed on it. Plooster and Fukuta (1'7S)