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<br />-. <br /> <br />results were in agreement with selected case studies offield observations. Wind characteristics were also <br />shown to be important for successful targeting. <br /> <br />CONCLUSIONS <br /> <br />The purpose of this paper is to describe the general character of transport and diffusion of valley-released <br />AgI under various stability regimes observed in the Plateau region. Five sounding types were partitioned <br />from the 92 soundings taken during the Utah/NOAA AMP 1991 and 1994 field programs. The five <br />composite soundings covered a reasonable span of reality. The Clark model was initialed by each class <br />and run using stimulated releases of AgI from 3 valley sites. <br /> <br />There are several factors highlighted by the modeling applied in this investigation, most of which were <br />confirmed by field observations. <br /> <br />. <br /> <br />There is a frequent tendency for a low-level northward drift of valley-released of AgI in the <br />Sanpete Valley. <br /> <br />. <br /> <br />Under some circumstances there can be a westward or northwestward drift of AgI in the .Sanpete <br />Valley in spite of organized westerly flow aloft. <br /> <br />. <br /> <br />Strong upward motion over the lee slopes in possible under some stability and speed conditions <br />because of gravity wave transport. <br /> <br />* <br /> <br />. <br /> <br />Mechanical forcing is important for transport over a barrier. <br /> <br />. <br /> <br />Targeting from valley releases is poor for classes D and E which comprise 18% of the soundings <br />released during the 1991 and 1994 field programs. <br /> <br />· . Though properly targeted, the effectiveness of the AgI can be handicapped by warm temperatures <br />over the Plateau. This was particularly true for class D which comprises 5% of the soundings. <br /> <br />. <br /> <br />Class A appears to hold the best prospects of effective cloud seed because of the successful <br />targeting and characteristic cold temperatures. Thirteen percent of the soundings were class A. <br /> <br />A clear transport and diffusion categorization was evident in the modeling results, implying that modeling <br />of this type could be useful for operational planning. For example, model runs could be made at locations <br />being considered for seeding as demonstrated by Farley et aI. (1997). The application of the model. must, <br />however, be tempered with interpretive skills. The sensitivity of the model results to wind direction and <br />speed complicate the formation of generalizations. To estimate specific details of a case through <br />modeling, it is preferable to model individually, initializing with the most detailed parameters available. <br /> <br />. <br /> <br />84 <br />