WMOD00299

• Title: Physical Structure of Northern Colorado River Basin Cloud Systems
• Date: 9/1/1985
• State: CO
• Weather Modification - Doc Type: Report

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7

became available to acquire the large quantities of data needed to
determine the structure of the natural cloud systems. The purpose of
this section is to review what has been learned about the physical
structure and evolution of natural cloud systems occurring over the
mountains of the western United States. These cloud systems can be
divided into two broad groups, coastal mountain ranges (Sierras and
Cascades) and inland mountain ranges (Wasatch and Rockies).

A. Coastal mountain ra~es

Operational and research programs to augment precipitation along

the west coast of the United States have had a long history. Yet few

research programs until recently have emphasized the study of the

natural cloud systems which effect the region. Six significant weather

modification research programs have been conducted in the coastal

regions since the late 1950's. These include two in Santa Barbara County

(Neyman et al., 1960; Elliott et al., 1971), three in the central Sierra

(the Pyramid Lake Program (Squires, 1977), the Central Sierra Research

Program (CENSARE) (Rowland et al., 1973), and the Sierra Cooperative

Pilot Project (SCPP) (Reynolds, 1984)), and a program in the Cascades of

Washington (Cascade Atmospheric Water Resources Program (CAWRP) (Hobbs

et al., 1975b).Of these programs, three (CENSARE, CAWRP, SCPP) have

attempted to characterize some aspects of the natural state of the cloud

systems. TWo (CAWRP, SCPP) have made this a major component of the

program.

(1) CENSARE

The CENSARE program utilized randomization to determine

statistically the effects of cloud seeding in the central Sierra.

Significant efforts were made to classify storms based on their synoptic