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<br />. <br /> <br />. <br /> <br />1. INTRODUCTION <br /> <br />. <br /> <br />This report covers the activities of North American ~reather <br />Consultants (NAWC) and its two subcontractors - John Flueck <br />Associates and Sierra Hydrotech during the period October 1, <br />1982 through August 31, 1983. This report is the sixth in <br />a series of seven reports covering a multiyear contract between <br />the Bu rea u of -Rec lama t ion and NAWC. The con t rac t bE~g an in <br />1977 and continues into 1984. The main objectives of NAWC's <br />contract with the Bureau are the continuing design of the <br />Sier ra Cooperative Pilot proj ect (SCPP), the review of opel:ations <br />versus the design, and the evaluation of thE! effects of seeding <br />on the SCPP. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />After several years of preliminary ~tudies and calibration <br />seeding trials on the SCPP, a phased exploratory research <br />program was initiated on SCPP in the 1982-83 season. The <br />exploratory phas! of the program consists of randomized seeding <br />of post-frontal convective clouds occurring in winter storms <br />affecting the American River Basin of the Sierra NE!Vada range <br />in California. This exploratory research includes randomized <br />aerial dry ice seeding of post-frontc:Ll convection clouds (SCPP-l) <br />that meet certain microphysical criteria. The clouds are <br />typically seeded in a "formation zone" that normally occurs <br />over the foothill regiDn of the Sierra Nevada. Effects of <br />seeding are documented in a chain of events approach beginning <br />with cloud physics aircraft response variables, continuing <br />into digitized radar observations, and ending with precipitation <br />measurements on the ground. Unfortunately, the 1982-83 winter <br />proved to be an exceptionally wet one with the result being <br />that only one randomized SCPP-l test case was acquired during <br />the January through March experimental period. ValuablE~ background <br />data were, however, collected (without any project seeding <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />1-1 <br /> <br />. <br />