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<br />e <br /> <br />orographic), EB (embedded bands), MB (major bands), CT (convective trains), <br />C2 (cells of more than one-half coverage), and C1 (cells of less than one- <br />ha 1f coverage). These types normally occur in the above sequence dur i ng <br />passage of a frontal system. C1 and C2 typically occur postfrontally and in <br />closed lows. They became the focus of attention because observations indi- <br />cated they contained more 1 iquidwater than ice, which is a major indication <br />of microphysical seedability. Descriptions of analyses and preliminary <br />design work can be found in . contractor reports by Marwitz et al. (1979), <br />Stewart and Marwitz (1980), Parish et a1. (1981), Pace (1980), Karacostas <br />(1981), Marwitz (1981), Elliott et al. (1978a, 1978b, 1979, 1980, 1981), Rhea <br />and LeCompte (1979), Rhea et a1. (1980, 1981), Solak et a1. (1981), and <br />Vardiman (1981). <br /> <br />Throughout the 4 years of preliminary data collection and calibration seeding <br />trials, a considerable amount of reduction and analysis of the above data <br />were conducted. However, due to the mass i ve amount of data co 11 ected and <br />the limited time for analysis, it was decided to conduct only limited field <br />activities in 1980-81 and devote the major effort to analysis and design <br />considerations. Two analysis conferences and four workshops were conducted <br />during the year. Proceedings of the two analysis conferences were published <br />and numerous papers were submitted for AMS (American Meteorological Society) <br />conferences and journals during the year. The original design document was a <br />direct result of the analysis year. <br /> <br />E. Design for SCPP-1 <br /> <br />Two design workshops were held in January and February 1981 to develop <br />experimental scenarios as the most likely meteorological conditions to be <br />selected for an exploratory experiment. Cellular convection (C1 and C2) was <br />identified as the most-likely candidate because it showed: (1) the greatest <br />probability of containing supercooled water, (2) the least probability of <br />containing high concentrations of ice crystals, and (3) the greatest degree <br />of turbulent diffusion to disperse seeding material. Following the analysis <br />conference in May of 1981, approval was given to complete the design of an <br />exploratory experiment on cellular convection and to initiate a shakedown of <br />such an experiment in the wi nter of 1981-82. Fl ueck (1982) presented a <br />general guideline for the design of weather modification experiments which <br />was used extensively in the design of SCPP-1. <br /> <br />F. SCPP-1 Shakedown <br /> <br />e <br /> <br />The shakedown for an exploratory precipitation augmentation experiment was <br />conducted in the winter of 1981-82. Equipment and procedures were tested for <br />suitability over the central Sierra Nevada. Dry ice seeding was conducted by <br />aircraft in postfrontal convection over 3-hour time blocks along 20-nmi legs <br />parallel to the mountain barrier. Observations were made by aircraft, radar, <br />and precipitation gages following seeding to measure seeding effects. <br /> <br />Ten experimental units were obtained during the shakedown season. In our <br />desire to quantify seedability as defined in the "Glossary" the experi- <br />mental units were classified into three categories of seeding potential. <br />The greater the amount of supercooled liquid water in a cloud and the ~ <br />fewer the ice crystals, the greater the seeding potential is believed to <br /> <br />6 <br />