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Show were of basically two forms : (1) detailed cas e studies u sing a ll avai l able data typ e s, and (2) statistical analys is of pr ecipi tation data under var i ous data stratifications. ! 1. 5 Summary of Conclusions The detailed case study analyses of 1968-69 data yielded strong evid enc e of positive seeding effects in seve ral individual cas~s, and unequivo call y pro ve d that (1) silver-in-precipitation concentration was notably higher in se c dC'd, as compared to unseeded periods, (2) silver iodide particles did, in fact, serve as active ice nu c lei, and (3) se e d e d snow crys tals were pr e dominantl y small hexagonal plates. The statistical analysis of 1968-6 9 rfata consisted of a non-par a m et ri c sum of squared ranks test (Mielke, 1967), applied to each individual station's ' optical snow sensor record after a series of stratifying routin e s had been imposed. Results showed statistically significant precipitation increases at Rabbit Ears Pass for cloud top temperatures ~:: -20°C, and decreases for colder conditions. This result is in agreement with reported work of Grant, e t. al. (1968). The study demonstrated the usefulness of sev e ral supporting measurements and te c hniques. ln particular, the methods for d e t e cting silver in snow and silv e r iodide nuclei in snow crystals were invaluable in interpr etation of experimental results. The diffusion tests and numerical modeling of orographic flow and precipitation both led to increased understanding of seeding requirements for orograp hic precipitation. It has been concluded that an operational seeding pro g ram should include both ground and airborne delivery systems. Criteria for seeding and choice of seeding technique were developed on the basis of the combined experimental results. It has been concluded that precipitation increases of 100% or great~ c ould be achieved for the Park Range, when cloud top temp e ratures are warmer than -20 °C, by using a combination of g round and airborne seeding. Given perfect predictions of cloud top temperature, d e trimental seeding effects produced when cloud temperatur e is l ess than -2 4°C could b e eliminated. For reasonably attainable cloud t emp e r a tur e p r e diction c apability, it is e stimat ed that a s e asonal c umul ative seeding effeci of 2 5% increase in precipitation could be achieved in p r actice . 1. 6 Report Outline Section 2. 0 of this report describes the fi e ld ope ration s·, equipment, and techniques that were used in the Park Range experiment s. Instrume ntation and methods developed specifically for this program are presented in detail. Section 3. 0 describes, and summarizes the r e sults of, supporting studies, 5 |
