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I I I I I I I I I I I I I I I I I I I Potential varies for precipitation augmentation on the various storm systems described. Additionally, the potential is storm-phase dependent as in other areas such as California as noted in the S'ierra Cooperative Pilot Project (Reynolds and Elliott, 1985). The overall modification potential per system type, estimated at this time, is given below. The A-1 system leads to deep, cold clouds which are naturally efficient precipitation producers. Although this type often produces large quantities of precipitation, it does not occur as frequently as the A-2 type. The A-2 system probably possesses more potential for augmentation than the A-1 type. It is usually a more inefficient precipi- tation producer because it carries less moisture and generally, somewhat warmer air. Storm type Relative potential A1 l~ A2 low to moderate B1 moderate to high B2 low to moderate The B-1 system is sufficiently cold and wet to have augmentation potential. It is likely to contain embedded wet conve!ctive clouds. At other times it produces the more stable orographic cloud regarded by some to be the most treatable cloud. The B-2 system will be warmer than the B-1 type but generally sufficiently cold for cloud trealtment. At times, moisture may be deficient in the B-2 system since it is usually accompanied by weaker winds. 4.2 Upper air data Of importance to this study is knowledge on the state of the atmosphere from the ground surface to the top of the uppermost layer which leads to wintertime cloud formation over and near J~rizona mountains. The pre- vious section of this report discussed, in a general sense, weather systems that frequently lead to precipitation events over the mountains. This section covers the study of availabl,~ upper air information collected by rawinsonde (balloon) ascent. The upper air data contain 26