Research on Increased Precipitation by Cloud Seeding: Development Phase

Development of several instrumentation systems for measuring atmospheric variables related to winter orogaraphic cloud seeding was undertaken. A heated tipping bucket precipitation gage was modified both for reliable use and accuracy of data. A solid state memory device was also developed at UWRL for this project. A parachute dropsonde for measuring vertical air motion was further developed. In addition, instrumentation was placed on board an aircraft for measuring concentrations of super cooled water, ice nuclei, and ice crystals. Airborne measurements during cloud seeding with silver iodide showed that the plumes of seeding material could be detected over a target area, and that basic factors involved with precipitation could be measured. That is, measurements of vertical motion, concentrations of super cooled water and precipitation size ice crystals along with precipitation on the ground gave a reasonable picture of the gross features of orographic storms. Indications of seeding effects were found only very tentatively. Further study and development are planned in order to better identify seeding effects.