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<br />used as a tool to predict the onset of- supercooled water events when storms with <br />these char'acteri st i cs impact the Si erra Nevada. However,' the pre-frontal <br />'. regions of ~tor{J1s ~ith meridional. flow characteristics are more difficult to <br />forecast. The lower clouds in these cases'are frequently obscured .by ~irrus <br />clouds on satellite photographs, making the onset of the storm difficult to <br />predict. <br /> <br />Another important aspect of cloud seeding opportunity in addition to the <br />existence of supercooled water is 'its magnitude. Seventy percent of the time <br />that radiometric measurements of supercooled water were above background, values <br />below 0.20 mm (Figure 23). Ninety percent of the time the measurements were <br />below 0.40 mm. It is not clear whether measurements at or below these values <br />represent true cloud seeding opportunity. Definitive studies are still required <br />to clearly interpret the meaning of these measurements in terms of the actual <br />cloud supercooled water content. To date, attempts at such studies have met <br />with limited success (see Heggli, et al., 1987b). <br /> <br />The highest terrain in the vicinity of Kingvale is 2.7 km. The rawinsonde <br />measurements presented in Section !5 imply that supercooled water-bearing cloud <br />layers are generally within 1 km of the highest terrain. This is the layer most <br />influenced by forced ascent. The temperatures of water saturated layers were <br />. often found to be within the range required for silver iodide activation. These <br />data indicate that, based on supercooled water presence in storms and the alti- <br />tude and temperature of water-saturated layers, the opportunity frequently <br />exists to use seeding to augment precipitation in Sierra Nevada. <br /> <br />ACKNOWLEDGEMENTS <br /> <br />This work was supported in part. by U.S. Bureau of Reclamation contract <br />4-CR-81-03860 to Electronic Techniques, Inc. The authors would like to thank <br /> <br />33 <br />