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I I I I I I I I I I I I I I' I I I I I Table 5. Summary of 1994 NOAA/Utah K.,-Band Radar Operations DATE: TIME PERIOD (MST) OPERATION DESCRIPTION 10 March 1400 - 1704 Chaff tracking experiments in southwesterly flow with natural echoes from midlevel clouds. Releases from AHS at 1430-1450 and 1540-1600. Files d940310.14 - d940310.16. 11 March 0700 - 0922 Marginal storm conditions; no experiments. Files d940311.06 - d940311.09. 15 March Radar removed from RRS. End of field program. F. Srlow Samples for Ag Analysis The use of chemical analysis of snowfall has frequently been used to determine whether cloud seeding operations using Agl as an ice nucleant are successful in targeting a particular watershed. Since! silver is nearly nonexistent in natural snowfall, the detection of silver concentration above a background level of about 4 x 10-12 g ml-1 gives an indication that Agl is being incorporated into the precipitation process. The detection of Ag alone, however, does not necessarily mean that Agl is acting as a nucleant, since Agl can also be scavenged by cloud droplets and captured by snowfall through the riming process. The presence of silver above background does provide good evidence that the region being sampled is bein~1 successfully targeted during those periods when silver is present. Super and Huggins (1992) reported on the use of this technique to evaluate seeding from ground based generators upwind of the Wasatch Front and the Wasatch Plateau during the winter of 1990. With the generator placements used that season, silver was found in snowfall relatively infrequently. The technique was used again during the 1994 NOAA/Utah field program to help assess targeting during the seeding experimEmts. In contrast to the bulk samples collected following storms in 1990, time sequential samples were collected iln 1994 at the project target site (TAR). This procedure was used during the 1 Sl89 NOAA/Utah field program, and results are 24