The Blanket Effect is intended for others to learn about weather modification and its related subjects in an easy to understand way. Started in 2005, this blog is a work in progress as the technology advances

December 21, 2006

Cloud Seeding Manual Pt. 1

(note: An amazing find is a scanned copy of the research paper shown below at the University of Washington's Digital Collections website. Excerpts of the first 2 pages of the paper have been reproduced. For all parts of this series, click "CENSARE Cloud Seeding Manual link-editor)


in association with the United States Department of the Interior, Bureau of Reclamation, Fresno State College Foundation Fresno State College Fresno, CA

CENSARE Cloud Seeding Manual

Pg. i - This volume discusses the procedures used in conducting cloud seeding operations for winter orographic precipitation augmentation purposes on the CENSARE (CENtral SierrA Research) Project, criteria and techniques for targeting the effect, optimal conditions for seeding, recommended revisions in seeding systems and operations, and further research needs.

The seeding was conducted on an experimental basis in the upper portions of the Mokelumne and Stanislaus river basins in the central Sierra Nevada of California during 1969-1972. (image right from, click image for detail)

This research was sponsored by the United States Department of the Interior, Bureau of Reclamation, Division of Atmospheric Water Resources Management, under Contract No. 14-05-D-6592, dated 1 July 1968, as amended.

I. Introduction:

pg. 1: Research Investigations of ways to increase water supplies in the Sierra Nevada of California through weather modification have been underway for a number of years.

The CENSARE (CENtral SierrA Research) project was conducted by California State University, Fresno Foundation, Atmospheric Water Resources Research (AWER) during Fiscal Years 1969 through 1973 as part of the Bureau of Reclamation's “Project Skywater”.

Activities on the CENSARE project consisted of both field experimentation and office studies, and were designed to provide criteria and procedures for he optimized conduct of weather modification operations.

The project's cloud seeding target area consisted of the upper portions (above the 5,000 foot elevation) of the Modelumne and Stanislaus river watersheds.

Primary emphasis was placed on modification of winter season storms occurring between November 15 and April 15.

Field experimentation consisted of actual cloud seeding operations and extensive meteorologic surface and upper-air observations.

Analyses of the upper-air data were performed to determine vertical and horizontal atmospheric motion during storm periods.

These analyses, in conjunction with several other methods of evaluation, were used to determine the area and type of precipitation effect resulting from different modes of seeding under various meteorologic conditions.

The intent of this manual is to describe:

-Seeding generator systems used during this experimental project,

-Requirements for targeting the seeding material and effect,

-An example of actual seeding operations,

-Optimized cloud seeding meteorological conditions,

-Seeding system recommendations for future operations, and

-Recommend areas of continued research.


Precipitation augmentation through cloud seeding is based on providing artificial condensation nuclei to super-cooled portions of clouds which are deficient in natural condensation nuclei, or to warmer portions of clouds (-15C to -5C) which produce minimal precipitation under natural conditions.

The artificial nuclei attract the super-cooled cloud water vapor, causing it to condense into an ice crystal around each nucleus.

The nucleated crystals then continue to grow until either they are large enough to precipitate out, or the cloud water vapor has been fully utilized.

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