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Silver iodide can be produced from a wide variety of generating devices. Liquid-fueled generators have proven cost effective and reliable on many projects and therefore were recommended by Reclamation for the demonstration project. The seeding agent recommended was a 2AgI-NaI (silver iodide - sodium iodide) solution in acetone. This seeding agent has been used for over 30 years in almost all countries engaged in precipitation augmentation activities. Experience has shown that the 2AgI-NaI solution is relatively easy to handle and produces few operational problems. However, the primary reason that 2AgI-NaI was recommended, rather than another AgI solution, was to minimize the uncertainties in the nucleation stage of the seeding process. Nuclei produced from it nucleate ice by the condensation-freezing mechanism at a rapid rate that is independent of liquid water concentration, which was a relatively unknown quantity in Moroccan clouds. Moreover, if supersaturated conditions are encountered, as might be the case in the orographically ascending air and the embedded convection, the nucleation rate might be even faster. Various strengths of AgI solutions have been used on precipitation augmentation projects around the world. The seeding agent used during the 1984-85 and 1985-86 field seasons was an AgI-AgCI (silver iodide - silver chloride) solution containing 4 percent by weight of AgI. This solution caused some technical problems to the Lohse airborne generators, including nozzle obstruction. To avoid those critical problems and to minimize the uncertainties in the nucleation stage of the seeding strategy, Reclamation recommended that a solution of 2AgI-NaI (silver iodide - sodium iodide) containing 2 percent by weight of AgI be used in the following field seasons. This recommendation was adopted. A seeding rate of about 200 g AgI per hour per Lohse generator was set; this was achieved by a burn rate of about 11 liters of solution per hour. Reclamation's recommendation that a 2-percent rather than a 4-percent solution be used was based on the high probability that burning the stronger solution would not substantially change the number of nuclei obtained; rather, coagulation would result in the production of larger nuclei (Dennis, 1980). As the nucleation rate of 2AgI-NaI is independent of particle size, the only advantage of a 4-percent solution would be the very slight increase in nuclei output, which was judged not to be cost effective. 2.4 Scientific Operations Plan Cloud seeding operations were conducted by the DMN's Division of Research in Casablanca. The project's operations team consisted of more than 50 trained meteorologists, meteorological technicians, and electronics technicians located from Casablanca to Khouribga, Beni Mellal, and AziJal. The operations team w.as assisted by a scientific team of six meteorologists located in the project's analysis center in Casablanca. FRA pilots and technicians for the seeding aircraft were stationed with the aircraft at bases near Meknes and Kenitra. The on-duty operations director guided aircraft and ground-based seeding operations using data from a 5-centimeter weather radar at Khouribga, an upper air sounding system at Beni Mellal, a satellite downlink at Casablanca, and near real-time meteorological and visual observations from the project area. A detailed operations plan outlined the specific decisionmaking criteria (including suspension criteria) and operational procedures for aY aspects of the project from the declaration of project status to opportunity recognition, conduct of cloud seeding operations, instrumented aircraft cloud physics research flights, and data collection (Hartzell et aI., 1986). 14 I I I I I I I I I I I I I I I I I I I