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000175 both ground and airborne releases. These data will be used to calibrate computerized diffusion models specific for each subbasin. The model results will help quantify the number of ground sites and aircraft required to provide the optimum concentration of nuclei to the cloUdS, and the conditions under which each type of seeding can be used. b. Establish characteristics of acceptable ground generator loca- tions. It will be critical to identify siting criteria for each subbasin which will ensure that generators will be positioned so the nucleating agent will be reliably transported into the desired cloud regions in appropriate concentrations at the required times. The T&D studies will be accomplished using stationary or mobile ground- based generators as well as seeding aircraft to provide nuclei and instrumented aircraft to trace the resulting plumes. Additional data will be collected using networks of surface sensors to measure such parameters as wind velocity, wind direction fluctuations, and distri- butions of surface temperatures. Observations will be obtained under the ranges of winter meteorological conditions usually experienced. Resulting information will be analyzed and model outputs used to establish networks of ground generators, and airborne seeding flight tracks. - 2. Opportunity recognition. - Seeding opportunity recognition studies will concentrate on identifying, at all subbasins, those meteorological conditions under which seeding is expected to produce increases in precipitation. The investigations will focus on identifying those storm periods during which available supercooled liquid water is not being efficiently converted to precipitation-sized ice particles. The end result will be development of a refined scheme for timely response to the presence of unused liquid water with the appropriate seeding application. Data will be collected from surface, aircraft, and satellite sensing platforms. The information from all sources will be integrated and analyzed to produce short-term "climatologies" of such parameters as: supercooled water presence and quantity, precipitation occurrence and amount, distribution of ice crystal concentrations in storms, occurrence of storm types, cloud heights, etc. The results will be used to establish the network distribution of sensors necessary to provide real-time information on which seeding strategy decisions will be based. The climatological information will also provide estimates of the number and duration of treatable events expected to occur during a typical winter season. This will influence planning for the supply, equipment, and support contracts required for subsequent Basin-wide operations. Seeding delivery and opportunity recognition systems that are specified as a result of the transferability studies will be tested to confirm their operational effectiveness. The basic approach will be to use airborne and surface instruments to detect and monitor alterations in the microphysics occurring as a direct result of carefully prescribed seeding treatments. For example, pulses of seeding material may be used during somewhat stable conditions to directly observe the physical 34