WMOD00307

• Title: A Proposal for Cooperative Weather Research Between the Santa Barbara County Water Agency and the US Department of Interior Bureau of Reclaimation in the Context of the Weather Damage Modification Program through the State of CA 2002-2003 Winter Season
• Date: 10/17/2002
• State: CA
• Weather Modification - Doc Type: Report

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TABLE 1.
Historical Cloud Seeding Activities
in Santa Barbara County (1950-1974)

Rainy
(Winter)
Seasons Coverage Sponsor Purpose
Most of Upper Santa Ynez City of Santa Barbara and To increase
1950-51 Drainage Basin Montecito CWD precipitation and
runoff
1951-52 and Santa Barbara County Santa Barbara County Increase yields of
1952-53 Water Agency watershed
Early 1955 Santa Barbara County Santa Barbara County Increase yields of
Water Agencv watershed
1956-57 Santa Barbara County Joint venture of nine Randomized seeding
through and Ventura County agencies
1959-60
1967-68 Santa Barbara County U.S. Naval Weapons Special research
through (north of Santa Ynez Center (randomized cloud
1973-74 Mountain Range) seeding)

Atmospherics, Inc. conducted a program during the 1997-98 winter season and Weather
Modification, Inc. conducted programs in the 1999 through 2001 winter seasons. NA WC
conducted a program in 2001-2002 winter season and is scheduled to conduct a similar program
in the 2002-03 winter season. An overview of the design of this program is provided in section
1.3.

1.2.1 Theory and Previous Research Results

Two approaches have evolved concerning the potential to augment precipitation. One theorizes
that a natural cloud's efficiency to produce precipitation can be increased by altering the cloud
microphysics, while the other postulates that seeding can result in the release of additional latent
heat, leading to increased precipitation. The first theory has often been referred to as the static
seeding hypothesis while the second relies upon dynamic effects of cloud growth. In many
situations both processes could be operative, whereby a cloud's precipitation efficiency is
increased and the cloud is also made to grow larger due to the seeding.

In modern-day cloud seeding programs the typical seeding agent is a silver iodide (AgI)
complex. Discoveries in the late 1940's established that minute particles of silver iodide, when
injected into a cloud composed of supercooled water droplets, would cause those droplets to
freeze (Vonnegut 1947). Supercooled water droplets (cloud droplets that remain liquid at
temperatures <OOC) frequently exist in clouds as evidenced by icing on aircraft.

Weather Damage Modification Program 5