WMOD00294

• Project Name: Project Skywater - Sierra Cooperative Pilot Project
• Title: The Design of SCPP-1 - A Randomized Precipitation Augmentation Experiment on Winter Cellular Convection in the Central Sierra Nevada
• Date: 11/1/1983
• State: NV
• Weather Modification - Doc Type: Report

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VI. OUTLINE OF EXPERIMENTAL DESIGN

SCPP-1 is designed to test the statistical hypotheses set forth in section V.
The experimental design emerged during the 1979-82 period and was tested
during the shakedown season of 1981-82. Like all experimental designs, it
represents a compromise between the ideal experiment and that which can be
accomplished with available resources. This section provides an outline of
the experimental design; details are left to later sections.

The experimental unit length is a fixed period of 3 hours (dictated by the
duration of seeding). The beginning and ending times of this period will
vary from point to point within the target area based upon the extrapol ated
motion of the treated volume.

The target area for the SCPP-1 experiment includes the region bounded by
Interstate 80, the Sierra Crest, U.S. Highway No. 50, and the foothills of
the Sierra Nevada (fig. 6-1). It includes most of the American River Basin
above Folsom Reservoir and a very small part of adjoining basins. Seeding
effects are directionally targeted to the middle of this area.

The region downwind of the Sierra crest was not included in the target area
because it typically lacks clouds during SCPP-1 conditions. However, down-
wind effects in the Tahoe-Truckee region are studied using data collected by
the Bureau and the Desert Research Institute.

__ The treatment un it 1 ength is 1 imited to the first 3 hours after treatment
begins. The observational unit length will vary, depending on the obser-
vational system and the meteorological conditions. Samples are taken within
a Lagrangian reference frame. The objective is to sample conditions in space
and time to follow seeding effects as they move across the target area with
the existing cell motions.

Observations are made in advance of the treatment time for qual ification and
classification of experimental units. Data collected during each experi-
mental unit are used to calculate response variables and predictor variables
and for related studies.

For the primary response variables, the maximum distance downwind from the
seeding location that will be considered is that determined by 1 hour of
cell travel. For secondary precipitation response variables, measurements
will be made within the portion of the EPS (WhiCh varies from case to case)
whose upwi nd and downwi nd edges are determi ned by 1 hour and 3 hours of cell
travel (from the seeding location), respectively. Thus surveillance and
measurement systems must be operated over the area for a minimum of 6 hours
beyond the beginning of seeding. This will also allow adequate purge time
for the treated volume to move out of the target area.

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The three main observation systems for the experiment are a cloud physics
aircraft, the Skywater radar at Sheridan, and the precipitation gage network.
Each of the systems merely samples the experimental unit. No observation
system can measure the variables of interest over-the entire space and time
cont inuum. The preci pitat ion gage network can measure continuously in time

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