| OCR Text |
Show values against 16 October-2 8 February Steamboat Springs precipitation was prepared for Rabbit Ears and Cameron Pass. These two stations are illustrative of the results of an extensive effort to isolate an effect using "conventional" data. Figure 205 is the plot for Rabbit Ears. A positive seeding effect would be indicated by points to the left of the dotted trend line of best fit. If is significant that all four seasons of seeding fall to the left of this line, indicating small positive effects. There is some evidence that on occasion the primary target was overseeded; therefore, stations downwind in the next major range were examined. Cam eron Pass results are plotted in Figure 206. Note that here, as in the Rabbit Ears Pass case, all four seeded seasons are well to the left of the trend line. There is a definite indication of a small total_net positive seeding effect. Another study of snow course data involved the use of several Wyoming snow courses, just north of the Park Range area, used together as a control s et to look for possible large area and downwind effects of seeding in the Park Range. The Wyoming courses combined as a control were: Battle Creek No. 1 Old Bottle No. 1 Webber Spring Fox Park Ryan Park Evans 1 North French Creek North Barrett Creek Albany (1949) Rock Creek No. 1 (1959) The 1 April group mean water content and the percent deviation from the mean were computed for 1938-68. The same was done individually for a large group of Colorado (target) courses and the indicated effect computed as (target % deviation - control % deviation) for each year of record. These values were plotted and isoplethed. The charts for the four years of seeding are presented in Figures 207-210. The primary Park Range target area indicates a slight negative effect. There is a persistent positive anomaly on the west slope of the Medicine Bow Mountains in the vicinity of Cameron Pass and south. It occurs approximately fifty miles downwind, in at least qualitative agreement with the findings of Brown and Elliott (1968) and Bowen (1968). There is a second positive anomaly which occurs further south, and might possibly be attributed to seeding at Climax or Berthoud Pass. Anomalies were present in the plots for past years but were not in consistent areas. The anomaly shown in the 1966-69 plots is not unique, but it is indicative of a positive downwind seeding effect. The same technique was used for Fremont Pass data and results are indicated in Figure 211, for 1938-1969. Large increases in snowpack are not e vident. Figure 212 is a plot of the peak snowpack values for the special SCS Park Range Snow Courses normalized to Buffalo Pass. One significant fact here is that the Rabbit Ears snow course peak snow pack for 1969 is higher than 301 |
