WMOD00558

• Project Name: Project Skywater, Sierra Cooperative Pilot Project
• Title: Project Skywater, Sierra Cooperative Pilot Project - Fall 1984 Status Report
• Date: 12/1/1984
• Weather Modification - Doc Type: Report

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Data collection for SCPP began during the winter of 1976-77. The SCPP

field office was set up at Auburn, California in September 1977. SCPP

has been in the field each winter since then with the exception of 1980-81,

which was a stand-down year for analysis of the data collected during

the 3 preceding years. Cloud seeding experiments have been conducted

on SCPP since the winter of 1977-78, but on a limited scale and with

close attention to suspension criteria, which were designed to prevent

seeding during hazardous weather situations.

The next section of this report details the procedures used in conducting

the SCPP field operations, both past and present. Following this section

the major findings of these field studies will be reviewed and their

impact on planning for the next 3 winters of field operations will be

discussed.

2. SCPP Field Operations

2.1 Operational Programs

Operational cloud seeding projects to increase precipitation and runoff

from the Sierra Nevada have existed since 1948. Nearly all of these

projects have been based on the hypothesis that the precipitation rate

in a mountain storm can be increased by increasing the concentrations

of ice crystals in the clouds at temperatures warmer than about -200C.

This hypothesis is based on the observation that some clouds contain

liquid (supercooled) droplets at temperatures below OoC, and the fact

that ice crystals in the presence of supercooled cloud droplets grow

in a few minutes into small snowflakes. The additional ice crystals