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<br />in cloud-top temperature and rate of areal expansion of the cloud <br />top to determine rainfall. The technique has been applied to four <br />rain gage locations, and although the results were not significant, <br />additional studies are being made to take subcloud mixing and <br />evaporation into account. <br /> <br />. <br /> <br />IV. Application to the Sierra Cooperative Pilot Project <br /> <br />The Sierra Coop~rative Pilot Project (SCPP), a winter orographic <br />cloud seeding experiment, is now being designed by North American <br />Weather Consultants and the Bureau of Reclamation in the Sierra <br />Nevada of central California. Building upon what has been learned <br />both from within Project Skywater and from other projects, studies <br />are proceeding to determine what techn'iques are presently best for <br />measuring and collecting data. <br /> <br />Precipitation data collection systems now in use in the Sierra <br />Nevada by the Desert Research Institutl~, Sacramento Municipal <br />Utility District, Pacific Gas and Electric Company, California <br />Department of Water Resources, Forest Service, and National Weather <br />Service are being evaluated for the SCPP. During the present phase <br />of the SCPP, tests are being conducted using the Bureau.s digitized <br />5-cm radar, a line of recording precipitation gages along Interstate 80 <br />over Donner Pass, the University of Wyoming's cloud physics airplane, <br />and data from the SMS/GOES (Synchronous Meteorological Satellite/ <br />Geosynchronous Operational Environmental Satellite). <br /> <br />One objective of the radar data analysis is to infer precipitation <br />rates to derive usable Z-R relationships which can be verified with <br />gage measurements of precipitation rate. If this can be accomplished, <br />it is believed that the technique can be extended to provide estimates <br />of areal precipitation. Data obtained from the cloud physics aircraft <br />will also be used to make estimates of the Z-R relationships. For <br />those aircraft measurements taken over a precipitation gage when the <br />radar is scanning the same area, the calculated values of Z and R <br />can be compared to those observed. ~/ <br /> <br />The evaluations necessary to select a Ireliable gage capable of <br />providing accuracy within 0.254 millimeter (0.01 inch) and time <br />resolution of at least 15 minutes have high priority on the SCPP. <br />Comparative tests between large-orifice, high-capacity weighing <br />bucket gages and heated tipping-bucket gages are with possible <br />modifications expected to provide a satisfactory solution. <br /> <br />7 <br />