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I I I I I I I I I I I I I I I I I I I Nine of the sites are located at high elevations and sampling must be done by helicopter. The other sites are accessible by highway. The locations of the sampling sites are shown in fig. 3-7. Table 3-4 lists the station names and elevations. The sampling sites will all be identifiable by snow poles. Contact with Bureau staff wi 11 be made to obtain he 1 i copter support. It should be possible to sample all 16 sites in one day using two crews equally distributed from south to north within the target area. For the total season we expect to collect approximately 100 profiles. Each profile will contain, on the average, 15 individual samples (2 cm depth each), yielding 1500 samples for analysis. The vertical resolution of 2 em depth corresponds to approxima- tely 1 to 2 hours of precipitation depending on precipitation rate. Since each sampling site is colocated with a recording precipitation gauge this data will provide supporting information on times of occurrence of precipitation and precipitation rates. The chemical analysis of the snowfall collected from the sites wi 11 be con- ducted in the DR! clean room facilities in Reno. The data generated will pro- vide direct information on the transport of the seeding aerosols into the mountainous regions on both sides of the Sierra Nevada crest. The vertical distributions of the seeding chemical in the snowfall at anyone site provide information on temporal variations at that site. The differences in these distributions from site to site gives information on spatial dispersion of the aerosols throughout the storms and their subsequent incorporation in the snowfall collected from the site. Overall chemical content of the snow as a function of distance from the generator sources will be compared with GUIDE model predictions based upon diffusion, dispersion and nucleation of the seeding aerosols. II! -25