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Show tion is to be conducted efficiently. Perhaps the major problem in operating ground generators for cloud nucleation programs in mountainous terrain is the vagary of the transport and dispersion characteristics as discussed in the preceding section. The best treatment system presently available is a combination of aircraft and ground generator seeding, using the aircraft system to overcome inversion problems with the ground generators, and using the ground system to assist the aircraft system for long period treatments of a large volume. The use of a Nike or M-33 radar system as a tool for quantitative precipitation measurement under conditions typical of the upper Colorado River Basin presents some problems. First of all, the Z vs R relationships are not well established for the range of crystal types and riming conditions encountered. This does not, however, severely limit the usefulness of the relative values obtained. A very real problem, however, is the range limitation for low precipitation rates. A significant portion of the orographic precipitation is char- : acterized by low rates. Except in special cases, the practical limiting range is of the order of 20-25 kilometers. The radar is particularly suitable for use,' in zenith pointing and profiling modes near or in the target area. It is usually : not suitable for complete mapping of precipitation at extended ranges of greate1: than 40 - 50 kilometers. i In summary, upon reviewing our experience in the Park Range Program, these are the major operational problems encountered: (1) providing a uniform and predictable treatment of a given cloud volume with ground generators. (2) providing a practical scheduling of operations so that personnel are utilized efficiently and all desirable precipitation periods are monitored. echoes. 5. 8 1 (3) providing adequate mapping of orographic precipitation radar Seedability Criteria In order to develop seeding technology to the point where precipitation can be optimized, or to stratify data for analysis from indiscriminant seeding, a set of conditions for seedability is required. For operational optimized seeding, these conditions must be predictable or at least readily recognizable in concurrent time. On the basis of results from the Park Range program, a set of seedability criteria have been developed. The conditions for seedability established in this section are primarily theore- i tical, and the methodology is sufficiently g t:neral to be applied to other geo- 1 314 |
