WMOD00284

• Applicant: Thompson, J.R., G.W. Wilderson, and D.A. Griffith, North American Weather Consultants
• Sponsor Name: USBR
• Title: Cloud Seeding Data Collection, and Analysis Assoc. with the Colo River Augmentation Demonstration Program
• Prepared For: USBR, Divison of Atmospheric Research
• Prepared By: Thompson, Wilderson, Griffith
• Date: 12/1/1987
• State: AZ
• Weather Modification - Doc Type: Scientific Study

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This too, was shifted by about 9 hours from the Arizona data,
which peaked about noon.

Based on the limited two month data sample, the diurnal
variation of hourly precipitation occurred most frequently
during the daytime hours, peaking near noon. In addition,
the majority of the total precipitation observed over the
period of record also occurred in the daylight hours, primarily
between 0900 to 1500 MST. These findings are in contrast
to a similar analysis of diurnal precipitation variation on
the Grand Mesa in Colorado, where both the maximum frequency
of occurrence and maximum percentage of total precipitation
occurred at night. Clearly, more data needs to be acquired
in regard to the Arizona precipitation regime before any firm
conclusions in regard to the diurnal variation can be reached.

3.2.7

Precipitation Periods Within a storm (Episodes)

The presence of precipitation over the region is not
a guarantee that sufficient SLW is available for cloud seeding
to be effective, e.g., see episodes SS-9 and SS-10. But,
the fact that some precipitation is falling indicates the
presence of clouds and the analysis in Section 3.1 documents
that there were many instances when precipitation was falling
and considerable SLW was also present which might suggest
that some augmentation potential was present. At any rate,
the duration of precipitation can be of considerable importance
in planning future weather modification experiments or operational
programs.

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