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up\\ind and over Colorado mountain barriers arc pruperly seeded. increases in snowfall can be anticipated. Several examples of adequate T&D over the Grand Mesa. from both aircratl and high- altitude ground-~d Agl gen~rators. wcre publish~d by Holroyd et al. (IQ881. Observations of S(.-eding-cauSL-d increases in ic~ crystal concentnttioru; at cloud levels over the same barrier were shown by Super and Roe (IQ88). Some ofthcsc shon-term. physicaJl~'-bas(.-d S(.'t.'ding experiments inereased snov.fall at the ground. Similar "physical experiments" were conducted in central Utah as swnrnarizcd by Super (l999a). "Tne magnitude of sc.--cding-induccd sno\\ incJ"e"dSC..'S on a seasonal basis is still open to qU~1ion. and likely ranges from trivial to perhaps 10-15 percent the laner for properly conducted seeding. According to the: American Meteorological Society (1998). "Th\.'re is statistical evidence that precipitation from supercooled orographic clouds (clouds that develop owr mountains) has been seasonally increased by about 10%. The physical cauSt.'-and-cITcct relationships. however. have not oc>en fully documented. Nevertheless. the potential lor such increases is supported by field measurements and numerical model simulations." Rut much of the statistical evidence is based on questionable target-control applications discussed in the previous sc.'Ction. lne magnitude of any" seeding-induced change in snov.fall is highly dependent upon the s..."Cding methodology employed. While the la)-man may consider any fonn of cloud seeding to be similar in application and rt."'Sulls. that common view is unrealistic. ^ \\ide range of Agl (and other agents) set,.-ding deliver:" methods and release rates have been used. Then: is no reason to expect them 10 all produce ~imilar results. Silver iodide may be released from aircraft. using acetone generators. burn-in-plaec p)-TOtl..'Chnic narcs or \"Crtical drop nares. More common and Ics.<; expensive methods employ ground-hao;ed AgJ generators. Some projects USl..' radio-controlled high altitude ground-based generators 10 increase the chances of successful T &D of Agl into orographic clouds. ~10re commonly. projects have used manually..oJ>Crdtcd ground-based generators at relatively low elevations where local residents arc available to operate them. This latter approach is the most economical. but has the greatest uncertainties concerning T &D into clouds several miles dO\\l1\\;nd. and thousands of feet above. the generators. Each seeding method has a v.idc range of available Agl release rd.tl.."'S depending on individual seeding generator (or flare) output and crosswind spacing between generators (or nares). Obviously. higher release rates and closer spacing bct\\-.cen generators result in higher operational costs. With all this variability among projects. it would be quite surprising for resulting snowfall enhancements 10 be similar. Yet. similar seasonal increases. in the 5-20 percent range. have commonly been claimed whatever the seeding methodology. This limited range is difficult to reconcile with physical reasoning. ~1on.'O\'Cr. lack of snowfall augmentation is rarely reported by operational projects whatever seeding method is used. Weather moditication scientists arc well a\\1l.fC that Agl ctTl.'Cti\"enes.s is strongly dependent upon cloud temperature. Little physical (as opposed to statistical) evidence exists that Agl seeding has produced ml..-aningful 5no\\1'311 \\hen treated SL \\' cloud temperatures \\crc wanner than _sac to _9C:C. In order to be etlt.'Cti\'e. the Sl."t.-ding material must be routinely transponed into sufficiently cold SI.\V cloud and dispersed through large \"olurnes of cloud. in sufficiently high concentrations. Both ca1culalions and observations have ShO\\ll that concentrations of ctfective artificial ice nuclei ;