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DISCUSSION (latter portion of) The SF 6 was transported over the Wasatch .Plateau in these two cases with light surface winds observed in the upwind valley and at different locations on the windward slope. The SF 6 plumes reached temperatures levels considered to be effective for silver iodide nucleation in both cases (-12 and -17 0 C). Some of the SF6 plumes co-existed with low to moderate values of supercooled liquid water, another ingredient necessary for the production of a seeding effect. . . Examination of the individual stacked plots for the March 2 test case indicated that the SF 6 was frequently present in regions of supercooled liquid water. These regions appeared to be associated with upward vertical motion. It is therefore concluded that these regions were associated with convention. The SF 6 plumes were observed at 1500,;,1800 m above the Wasatch Plateau. Based upon observed SF6 concentrations, it is prob<;lble that these plumes reached higher altitudes. Table 4 indicates that the estimated cloud tops on March 2 were at 4 km. The plumes would have only needed to rise 250 m to reach the estimated cloud tops. Estimated cloud top temperatures were -14 oe. Silver iodide had it been --eo-released from the SF 6 site, could have produced more ice crystals than the calculated 27 crystals I-I if it was transported to the estimated cloud top heights. The March 6 test case was much colder than that of March 2. It was also a much weaker storm system producing only a few hundredths inch precipitation on the plateau. Aircraft observations of supercooled liquid water were either 0 or occasionally .10 to .20 g m-3. The Bureau radiometer at the UDOT site only observed a minimal amount of supercooled liquid water from 1600 - 1700 MST. The Desert Research Institute's mobile radiometer was operated along the Wasatch Plateau and also up and down Fairview Canyon. This mobile radiometer detected very little supercooled liquid water on this day except for a brief period from 1713 to 1728 MST. The mobile radiometer was driving down Fairview Canyon during this time. Liquid water values varied from .03 to .17 mm during this time. The Bureau radiometer on UDOT did not report any liquid water during this period. This period could have represented some seeding potential. This period was, in fact, being seeded from the valley based ground generator network as evidenced by NCAR counts considerably above background (several 1 O's of counts per minute). The .cold ambient temperatures at which the silver iodide nuclei resided should have resulted in nucleation whenever the nuclei encountered any supercooled water droplets. The angles of dispersion (the last column in Tables 4 and 5) from the SF6 ground based release point to the aircraft flights tracks ranged from 4 to 46 o. An average of the angles from the four SF 6 plume encounters in March 2 on the west track was 35 degrees. A similar average for the eight encounters on the west track for March 6 was 17 degrees. Most of the difference between the two days averages occurred due to a very wide SF 6 plume being encountered on the first two western flight legs on March 2 (40 and 46 degrees). It does not appear there is still more lateral dispersion of the SF 6 on the March 2 versus March 6 case. The difference could be due to much stronger convection that was encountered on March 6. An average plume spread angle for the two days on the western flight track was 23 degrees. . One important question that is not answered by this data set is whether multiple SF 6 releases from the valley generator network would merge over the Wasatch Plateau to form a relatively continuous "treated" volume. The NCAR counter data may provide some information on this question, but the lag time and flushing time of this instrument complicates such an analysis. A related question is, even if SF 6 and or Agl is released at multiple valley sites, do the resultant plumes disperse in a relatively uniform fashion over the Wasatch Plateau, or are they channeled up some of the canyons as these test cases might suggest? '- It is assumed that there is a uniform horizontal dispersion of AgI from the valley generators over the Wasatch Plateau, the mean SF6 plume angle of23 degrees can be used to estimate a desired spacing between the valley generators. The mean distance from the ground based silver iodide generators sites tQ 40