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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />simultaneously test a limited number of prestated hypotheses for confinnation, rather than <br />only a single one." Exploratory analysis can (and should) be conducted with the same <br />experimental data sets. Gabriel (1981) states that "An exploratory analysis . . . is one in <br />which no predetermined course is charted. The experimenter and analyst look for leads from <br />the data and follow them as far as they can." However, statistical inferences resulting from <br />exploratory analysis should only be considered suggestive, as no precise probabilities of error <br />can be assigned to them. Clearly, the confirmatory analysis is intended to provide "proof' that <br />seeding can enhance the multiwinter snowfall over a large target area with a high degree of <br />conclusiveness. Exploratory analysis is only intended to supplement the confinnatory analysis, <br />pointing the way to improving understanding in the future. <br /> <br />A final "definitive" statistical experiment for cloud seeding may be impossible to achieve. The <br />path to knowledge never ends (consider the long-term search for a "cure" for cancer), and <br />continued improvements in cloud seeding technology can be expected over the foreseeable <br />future. However, the proposed experimentation will place the technology on much firmer <br />scientific footing. Completion of the CREST program is fully expected to give potential users <br />considerable confidence in winter orographic cloud seeding in the Basin. <br /> <br />Physical investigations will continue throughout the statistical experiment, but at a lesser <br />frequency than during the direct detection phase. Investigations will include testing of the <br />statistical design and continuation of studies of cloud and precipitation processes. The physical <br />observations also will monitor proper operational conduct of the randomized program. For <br />example, measurements of ice nuclei concentration will test AgI generator operation. Tracer <br />gas tracking and chemical analysis of snowfall will test proper targeting. <br /> <br />Monitoring all key processes throughout all statistical experimental units is impractical. <br />Aircraft sampling, which would be expensive to carry out throughout every experimental unit, <br />is one limitation. Moreover, heavy airframe icing or severe turbulence will at times preclude <br />aircraft sampling at low levels over the target. Consequently, direct detection experimentation <br />must be limited to a fraction of the total time that orographic clouds are present. However, <br />plausible results from many direct detection experiments will add significant credibility to <br />statistical analysis. The combination of statistical results, backed by physical evidence and <br />numerical model predictions from a subset of the experimental units, will provide the scientific <br />evidence desired from the proposed program. <br /> <br />3A Site Selection Process <br /> <br />Two mountain barriers have been tentatively selected for the CREST experimentation: the <br />Grand Mesa of west central Colorado and the Wasatch Plateau of central Utah. Final selection <br />will be made only after appropriate NEPA (National Environmental Policy Act) and public <br />involvement processes are completed. The criteria and procedures used to select these locations <br />as the best experimental sites are discussed in detail in appendix A The experimental areas <br />will be on the eastern half of the Grand Mesa (fig. 2), and on the Wasatch Plateau in. the region <br />between the towns of Fairview and Price (fig. 3). Specific small target areas for direct detection <br />experiments will be chosen during the startup year of the program, in coordination with <br />environmental compliance activities. As discussed in section 4, the well-instrumented target <br />will be no wider than the crosswind extent of 1 to 2 seeding plumes (on the order of 5 km). The <br />target's alon.g-the-wind dimension will be investigated during the direct detection phase, but <br />will be less than the barrier widths, which are about 25 km. <br /> <br />15 <br />