WMOD00288 ‎(2)‎

• Title: Twelve Basin Investigation - Volume I
• Prepared For: Bureau of Reclaimation
• Prepared By: Robert D. Elliot, Jack F. Hannaford, Russell W. Chaffer
• Date: 5/15/1973
• Weather Modification - Doc Type: Report

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Figure 1. 2-11 is an example of the printer plots of lifted cloud top tempera-
ture versus precipitation rate. The curve plotted in O's represents the average
precipitation rate where the averaging interval is 1C. The curve plotted in *'s
represents the average precipitation rate where the averaging interval is 3C. At
points where the two curves intersect, ='s are plotted. Figure 1.2-12 shows an
example of the tabulated data from which figure 1. 2-11 was derived.
The data for these examples if for the Climax 2NW precipitation station in the
Central Colorado Rockies North Massif for the period of record before seeding began
at that site. These same data will b.? used for the rest of this section.
The program BMD02D from the UCLA Biomedical Computer Programs (Dixon 1971) was
used to produce scatter diagrams such as that shown in Figure 1.2-13. This is a
plot of lifted cloud top temperature against hourly precipitation rate at the Climax
2NW Station. The numbers plotted indicate the number of observations of hourly pre-
cipitation in the given category. After the numbers 1-9, the letters A-Z are used
to indicate successively higher frequencies. Figure 1. 2-14 shows an example of
another plot produced by the same program, this one relating an upper air parameter
(stability index) to the lifted cloud top temperature.
Figure 1.2-15 is a sample of the output from the third analysis program. The
average, standard deviation, maximum, minimum, frequency and relative frequencies
are calculated for each parameter by 5C intervals of lifted cloud top temperature.
1.2.8 Data Analysis. The results of the analysis of master files for each
massif were utilized in a systematic manner to arrive at an estimate of potential
incremental increase in precipitation. The plots of the various parameters versus
lifted cloud top temperature were examined to determine if there were any bias in
relation to cloud top temperature. The five degree block average soundings were
plotted on Skew T, Log P Diagrams for examination and the data key punched for the
area of effect computations. In certain instances there were modifications in the
average soundings and these are not,ed in Section 2 where applicable. If more than
one precipitation-CTT curve was available for consideration, the station considered
most applicable was selected although frequency of cases also entered into the
selection.
Once a precipitation-CTT curve was selected for analysis, a critical tempera-
ture was determined and the area of effect predicted not seeded and seeded curves
were adjusted to the station's historical curve as outlined in Section 1.2.1. The
remaining work consisted of calculating the percentage increase (at temperatures
warmer than the critical temperature and overall), the portion of precipitation in

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