WMOD00298 ‎(2)‎

• Project Name: Project Skywater
• Title: Project Skywater - Fiscal Year 1979 Report
• Prepared By: US Department of Interior Bureau of Reclaimation
• Date: 3/1/1981
• Weather Modification - Doc Type: Report

of aerosol chemistry, electron microscopic analyses, and the sources of
natural variability of aerosols related to precipitation mechanisms and
potential for seeding success are described. Among the more significant
results from the Miles City area were:

. Small cumulus clouds and cumulus complexes were found to contain high
particle concentrations and to have narrow particle size spectra;
broader spectra and lower particle concentrations were measured in
embedded cumulus.

. The growth of prec'ipitable particles is dominated by ice phase processes.

. Seeding small cumulus clouds and embedded cumulus from cloud top with
dry ice or silver iodide pyrotechnics to produce ice particle concen-
trations of 1 to lOlL may increase precipitation.

. It seems less 1 ikely that precipitation from tcumulus complexes could be
increased by seeding at the same rates.

.'

CONTRACTOR: South Dakota School of Mines and Technology, Rapid City,
South Dakota
CONTRACT NO. 8-07-83-V0009
PRINCIPAL INVESTIGATOR: Arnett S. Dennis
PERIOD: December 15, 1977 - Continuing
FUNDING: $319,104
PURPOSE: Design and evaluation of HIPLEX

The purpose of the work under the contract is to ensure the reliability and
sensitivity of randomized experiments carried out in HIPLEX and to perform
an evaluation of the HIPLEX program. These general objectives can be cate-
gorized into a number of intermediate objectives. Those pursued thus far
generally have centered on HIPLEX-1, the randomized cloud seeding experiment
which begain in the Miles City, Montana area, in 1979.

In fiscal year 1979, a number of objectives related to the design of HIPLEX-1
were completed, including: (1) development of criteria for selection of test
cases and seeding treatments, (2) identification of suitable response variables,
and (3) development of statistical tests and programing the tests for
routine application.

Intermediate accomplishments in 1979 include:

. Selection of 13 primary response variables and 8 secondary response
variables to test the physical hypotheses of seeding effects.

..

. Addition of snow content fields to the numerical cloud model, an
improved dry ice seeding subroutine, and testing of a HIPLEX cumulus
model with state-of-the-art microphysics on 12 HIPLEX cases.

. Development of theoretical procedures for evaluating HIPLEX-1 hypotheses
is continuing. Associated software is nearly complete.

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