WMOD00176

• Project Name: Annual Report
• Title: Seeding Operations & Atmospheric Research, 2005 Annual Report
• Prepared By: Duncan Axisia
• Date: 12/31/2005
• Weather Modification - Doc Type: Report

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I

The inception of the SOAR program
A ccmmitment to ccnduct sound scientific research & operations

Precipitation enhancement in the Southern Ogallala

Introduction

For over a hundred years we have drilled
through the dirt below our feet to reach the
water that is essential to our existence. That
waler, pumped from the Ogallala Aquifer, has
made the South Plains of Texas one of the
most productive agricultural regions in the
world. But that aquifer, the only water available
to agricultural producers, is being depleted at
an alarming rate in many areas. induding
Gaines, Terry and Yoakum Counties. All three
counties have declines of one 10 three feet
annually with five-fool declines observed in
isolated areas. Future projections for water
availability are not encouraging. Since the
aquifer that sustains livelihood is being
depleted and no surface water is available one,
of the few options presented to conserve
groundwater is rainfall enhancement by
weather moc!ification.

On 13 November 1946 Vincent J. Schaefer
dropped about 3 pounds of dry ice pellets from
a light aircraft into a supercooled doud in
western Massachusetts. Within about 5
minutes the cloud had turned into snowflakes.
which subsequently penetrated about 2000
feet into the dry air below the base before
subliming completely away. In 1947. Bernard
Vonnegut found that particles of silver iodide
could also generate large numbers of ice
crystals if the cloud is colder than about -5'C.
Many experiments followed showing that layer
douds wrth depths smaller than 1 km could
leave a cleared track that could reach a width
of 3km in 35 min and exist for more than 2
hours.

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Figure t Dry ice dropped from a seeding aircraft into
supettOOled clouds. Snow crystals were obsefved to fallout
of the doud ~aving a hole ....nere the doud water was
altered into ice preOpltabon. This is an example of cold doud
seeding, ...ner-e supercooled doud droplets are converted
into ice crystals. 'r'A1ich then po-edpitate out of the doud deck.
(USAF pholo: ooxed caption in the lower right reads "Effects
of seeding Alto--Strab.Js Oouds CIVef Green Bay, Labrado':
45 minutes after seeding with dry ice". Photo and boxed
caption obtained from Sewell. WRD.. el al" 1973:
Modifying the Weather: Western Geographical Senes, Vol.
9, Universrty01 VlCtona. Victoria. British CoIumtia, Canada).

The observation of seeding tracks visually,
such as shown in Figure 1. provided the basis
for embarking on extensive doud-seeding
projects for rain enhancement. Forty years
later, the discovery of satellite observed ship
tracks in thin marine layer clouds brought to
our awareness the coalescence-suppressing
effects of the pollution aerosol from the stacks
of ships.

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