A biennial systematic test of some newly-developed cloud-seeding nucleants,under orographic conditions

Summary A systematic cloud-seeding experiment was conducted in the Prenestine Hills, east of Rome, during the period of time Jan. 1966 – June 1968. The objective was to determine whether the use of monodisperse, electron-emitting giant condensation nuclei, and of giant Al₂S₃ ice-forming nuclei, both recently developed in our laboratories, could increase the precipitation over an area circumjacent to the site of aerosol dispersion. The method of evaluation involved comparisons of precipitation fallen during the week which followed the aerosolization of about 15 kg. of particulate matter, to the precipitation collected during the fortnight aftet that period. The results show that despite a relatively small amount of nuclei used per seeding operation, and notwithstanding an apparently handicapped design of data evaluation, the normalized and cumulated ratios of precipitation events, associated with those periods of time, indicate significant increases during summer and autumn, and significant decreases during winter season, over the area considered.