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<br />vely high, transient supersaturations and not to ice splinter ejection. <br />Another possibility for SICP is by ice particle fragmentation during colli- <br />sions between graupel and dendrites (Hobbs and Farber, 1972), between <br />graupel and rimed ice particles (Vardiman, 1978), and between filamentary, <br />low density rimed ice particles (Vali, 1980). Cloud studies have also <br />revealed SICP processes that do not seem to fit any of the above processes <br />(Hobbs et al., 1980; Hobbs and Atkinson, 1976; Cooper and Saunders, 1980; <br />Paluch and Breed, 1984). The reader is referred to the comprehensive <br />review of SICP by Mossop (1985) for a detailed discussion of this subject. <br />Since SICP contributes to the natural ice crystal concentration of a cloud, <br />it has a direct bearing on whether such clouds are statically seedable. <br />This matter will, therefore, be discussed further in the following section <br />on seedability. For the purposes of this review only the freezing- <br />splintering and rime-splintering processes will be considered in this <br />discussion but it should be remembered that SICP can occur in many other <br />ways over a wide range of conditions and they will have direct bearing on <br />the seedability of clouds as well. <br /> <br />The HIPLEX-1 experiment (Bureau of Reclamation, 1979; Smith et al., 1984) <br />was the first one to explicitly state, in advance, the specific precipita- <br />tion growth process that was to be optimized by glaciogenic seeding. It <br />was hypothesized that the efficiency of the IRG mechanism would be improved <br />by the prescribed seeding and thereby lead to both additional precipitation <br />and to an increase in the proportion of clouds that precipitate. <br />Statements of physical mechanism were, however, implicit in all static <br />seeding experiments conducted previously. In experiments conducted up to <br /> <br />7 <br />