Statistical Evaluation of Cloud Seeding Operations

Abstract

Abstract Modern commercial cloud seeding dates from the discovery in 1946 that silver iodide crystals are good nuclei for the formation of precipitation from cold clouds. Whether silver iodide seeding does actually increase the precipitation over what would occur naturally has been a controversial question. In 1953 Congress established the Advisory Committee on Weather Control, one of its responsibilities being to determine whether the United States should experiment with activities designed to control weather conditions. In its Final Report, 1957, the Committee concluded on the basis of historical records that in mountainous areas commercial seeding produced an increase of 10 to 15 per cent in precipitation. The methodology of the Committee's analysis is reviewed in this paper, and it is concluded that possible selectivity on the part of the seeding operator could produce fictitious results. The Committee's Report denies the existence of such selectivity but there is reason to doubt the denial. In the re...