Estimation of the effect of operational seeding on rain amounts in Israel

During the period 1961-75, two cloud seeding experiments were carried out in Israel. The first Israeli experiment had a two-target crossover design. The results indicated a positive seeding effect of 15%, significant at 0.9%. The second experiment indicated an enhancement of 13%, significant at 2.8%, in rain amounts in the northern part of Israel. Since November 1975, seeding in the north has been operational. The objective of this paper is to develop a method for estimating the seeding effect of the operational seeding. The proposed method is based on a historical logarithmic model of target precipitation on control precipitation. It is argued that the validity of the proposed approach stems from the stability of the relation between target and control precipitation over time, and the robustness of the meteorological system in the region. -from Authors