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<br />00u172 <br /> <br />liquid water along this path, limited inferences can be made with a <br />scanning antenna. The second system is a short wavelength radar <br />whose ultra-high sensitivity to cloud-sized particles and dual <br />polarization ice discrimination has great promise of filling in some <br />of the spacial (range gating) information not measured with the <br />radiometer. The third system is a remote icing rate meter now being <br />tested in the Sierra Cooperative Pilot Project. With this new <br />instrument it will be feasible to install a network of similar <br />devices on mountain crestlines to estimate the areal distribution of <br />supercooled water in the near-surface layer. <br /> <br />Accordingly, CREST will employ a hybrid approach for monitoring <br />supercooled water since no single device yields adequate estimates <br />of both its spatial and temporal distribution. The approach will <br />incorporate a network of remote icing rate meters together with <br />some microwave radiometers, short wavelength radars, and instru- <br />mented aircraft. This will produce the best portrayal of the <br />supercooled water field that is currently possible. These instru- <br />mentation advances are expected to make major contributions to both <br />the operational implementation and evaluation portions of the CREST <br />Program. <br /> <br />3. Statistical confirmation. - The final result of the CREST Program <br />will be the amount of water actually produced by the cloud seeding. <br />The randomized seeding will permit an unbiased, statistically signifi- <br />cant conclusion on the amount of augmented precipitation. Conventional <br />precipitation-runoff relationships and watershed models will then be <br />used to convert the precipitation increment into the additional water <br />produced. <br /> <br />Each demonstration project will be seeded on a randomized basis with a <br />portion of the treatment units left unseeded. The randomization <br />procedure and the treatment unit will be chosen to balance the require- <br />ment for maximum water production and for achieving confirmation of the <br />technology in the shortest amount of time. <br /> <br />The treatment unit will consist of a time period most representative of <br />the meteorological event being treated and will be objectively selected <br />for inclusion in the randomized program on the basis of real-time <br />measurements from the opportunity recognition system. Prior to each <br />demonstration program, a random list of seed and no-seed decisions will <br />be generated for each potential operational period. Block randomiza- <br />tion will be employed to prevent long sequences of the same decision <br />which could reduce the sensitivity of the evaluation. The seeded units <br />will be statistically compared with the non seeded or natural units so <br />that changes in the response variables can be evaluated. The response <br />variables will consist of measurements of key links in the chain of <br />physical events. As many key links as practical will be monitored. <br />The final response variable will be the precipitation amounts for each <br />treated unit. <br /> <br />31 <br />