Silver Concentration in Rainwater from Seeded and Nonseeded Florida Cumuli: 1973–1975 Results

Abstract

The main objective of the Florida Area Cumulus Experiments was to seed groups of supercooled tropical cumulus clouds to convert enough water to ice so that sufficient heat could be released to enhance cloud growth and augment rainfall over a specific south Florida target area. During three consecutive summers (1973?75), subprograms to monitor the rainwater silver concentrations were conducted. Results showed that rainwater silver concentrations can be detected in significantly higher concentrations in seeded vs nonseeded samples with a carefully positioned network and with precise care in the preparation, collection, handling, storage and analysis of the samples. In addition, the silver concentrations in the seeded rainwater samples are low enough to present no ecological or environmental problems whatsoever under the present seeding rates in south Florida. Stratification of the rainwater silver concentrations, using two different trajectory techniques, showed silver concentrations collected under continental influenced regimes to be almost identical to those collected under seeding conditions. This is a crucial result since, if rainwater silver concentrations are being used to determine whether the seeding material is being targeted in the optimum areas for maximum seeding efficiency, then the results may be biased under these continental influenced regimes.