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<br />analysis programs must be developed and contracts initiated where <br />required. Public involvement programs must be developed in <br />coordination with concerned Service Regions, the State of Colorado, <br />and a local citizens council. <br /> <br />The Preoperational Phase <br /> <br />Modification Hypotheses. The primary objective of the 2-year <br />Preoperational Phase (FY 1982 and 1983) is to develop a scientifically <br />sound and reliable design for the Operational Phase. In order to <br />develop appropriate physical hypotheses, a thorough understanding <br />of the synoptic, mesoscale, and micro scale processes that lead to <br />the formation of precipitation must be available. An intensive <br />physically-oriented group of design studies are required to achieve <br />this level of understanding. These studies will focus on: <br /> <br />1. Climatological studies of the synoptic situations responsible <br />for clouds and precipitation in the area <br /> <br />2. Acquisition of the understanding of the mesoscale organizations <br />and structures of the principal cloud and precipitation systems <br /> <br />3. The microphysical structures of the cloud and precipitation <br />systems <br /> <br />4. The capability for real-time recognition of and reaction to <br />seeding opportunities <br /> <br />These studies must be conducted with the best available instrumenta- <br />tion so the step-by-step cloud processes can be analyzed. <br /> <br />Experience in the Colorado River Basin and other project areas <br />indicates two classes of clouds have the most promise for <br />precipitation increase in the Basin. The first class consists of <br />certain parts of larger synoptic scale storms. The second class <br />includes locally-produced moist orographic clouds that are not <br />associated with large-scale disturbances. <br /> <br />In the first class, evidence from a limited number of airborne <br />cloud physics observations indicates that synoptic scale storms in <br />the San Juan Mountains generally consist of four phases: stable, <br />neutral, unstable, and dissipating (fig. 6). Each phase usually <br />lasts 6 to 9 hours. The storm normally begins with stable cloud <br />forming over the mountain barrier. The cloud is characterized by <br />low liquid water content and a high natural ice concentration. <br />Precipitation forms as a result of diffusional growth of ice and <br />occurs in relatively small amounts. During the neutral phase the <br /> <br />V-2 <br />