WMOD00430

• Title: A Diagnostic Technique for Targeting During Airborne Seeding Experiments in Wintertime Storms over the Sierra Nevada
• Date: 7/7/1988
• Weather Modification - Doc Type: Report

Reprinted from JOURNAL OF ApPLIED METEOROLOGY, Vol. 27, No.7, July 1988
American Meteorological Society

A Diagnostic Te,chnique for Targeting during .Airborne Seeding Experiments in
Wintertime Storms over the Sierra Nevada

ROBERT M. RAUBER

Electronic Techniques, Inc., Ft. Collins, Colorado

.

ROBERT D. ELLIOTT

North American Weather Consultants, Salt Lake City, Utah

J. OWEN RHEA
Auburn, CA 95603

ARLEN W. HUGGINS.

Electronic Techniques, Inc.,' Ft. Collins, Colorado

DAVID W. REYNOLDS

u.s. Bureau of Reclamation, Auburn, California
(Manuscript received 15 August 1987, in final form 24 November 1987)

ABSTRACT

A diagnostic technique for targeting during airborne seeding experiments has been developed for the Sierra
Cooperative Pilot Project (SCPP). This technique was used operationally during SCPP for real-time guidance
to aircraft, providing I) the location and orientation of the seeding line required to target ice particles created
by seeding to a specified ground location and 2) an estimate of the areal coverage of the seeding effect on the
ground. Procedures to use this technique as a real-time guidance tool during seeding operations in Sierra wintertime
storms are discussed.
Three evaluation studies of the targeting method are presented. These include I) comparisons of diagnosed
wind fields with those measured by aircraft; 2) comparisons of ice particle growth rates and habits within seeded
cloud regions with those used in the targeting computations; and 3) comparison of radar echo evolution within
seeded cloud regions with calculated particle trajectories.

1. Introduction

The Sierra Cooperative Pilot Project (SCPP) was
initiated by the U.S. Bureau of Reclamation in the
early 1970s to study the wintertime meteorology of the
Sierra Nevada, to identify conditions when cloud seed-
ing may cause changes in precipitation from wintertime
Sierra storms and to estimate the magnitude of those
changes (Reynolds and Dennis 1986). A specific pur-
pose of the SCPP was to develop new technology to
better identify seeding opportunities and appropriately
direct seeding efforts within Sierra Nevada river basins.

.. Present affiliation: Desert Research Institute, Atmospheric Sci-
ence Center, Reno, NV 89506.

Corresponding author address: Dr. Robert M. Rauber, Dept. of
Atmospheric Sciences, University of Illinois, 102 Atmospheric Sci-
ences Building, 105 South Gregory Ave., Urbana, IL 61801.

@ 1988 American Meteorological Society

A substantial effort was made in the SCPP to develop
a simple technique that could be used operationally to
target seeding effects during aircraft seeding experi-
ments. The purpose of this article is to describe this
technique and to discuss its utility in wintertime cloud
systems over the central Sierra Nevada.

2. SCPP Fixed Target Experiment

The Sierra Cooperative Pilot Project has been re-
viewed recently by Reynolds and Dennis (1986). The
SCPP operated within the American River Basin (ARB)
of the central Sierra. Figure I shows the location of the
major measurement systems within the ARB and the
topography of the region. SCPP aircraft, remote sens-
ing, and ground based instrumentation systems, in-
cluding all those used in this paper, have been discussed
by Huggins and Rodi (1985), Humphries (1985), Gor-
don and Marwitz (1986), Reynolds and Dennis (1986),
Heggli et al. (1987), and Marwitz (1987).