WMOD00509

• Title: Physics of Winter Orographic Precipitation and it's Modification - Summary of Presentations
• Date: 10/1/1985
• Weather Modification - Doc Type: Report

Summaries - Utah

1 . Introduction and Overview

This session was focused on recent findings from the Utah/NOAA Federal-
State Cooperative Program in Weather Modification Research.

The entire atmosphere of our planet works as an interactive system,
receiving energy from the sun and exchanging energy with sea, land and
space. A perspective for the relative scale of activities to enhance precipi-
tation in mountains, such as the Tushars of Utah, can be found through com-
parisons to other phenomena.

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Emissions from combustion are forecast to double the CO2 in the
atmosphere by the year 2050. Global scale inadvertent modification
of the atmosphere is expected through alteration of the earth's heat
budget by the CO2, and consequent feedbacks. This will impact the
water budget. The global circulation models of Manabe of the NOAA
Geophysical Fluid Dynamics Laboratory suggests that soil moisture in
mid-latitudes will be reduced by more than 20% in response to feed-
backs from the direct CO2 effects.

The El Nino phenomena includes substantial warming (1-20C) of the
sea surface temperature of the tropical Pacific, over areas greater
than that of the United States land mass. These warmed regions
alter the atmosphere's heat budgets and general circulation. The
very wet winters of 1983 and 1984 in Utah (and the Sierra Nevada),
and the Salt Lake floods are very well correlated with the peak of
the recent El Nino event. The Telecommunications must exist, but
are not yet clear enough to allow forecasting for a small region
(the previous El Nino event was not correlated with heavy precipi-
tation in Utah).

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Barnston and Schickedauz (JCAM) have found that agricultural irri-
gation in western Nebraska and adjacent states enhances the water
cycle. Their conclusion is that more evaporation enhances convec-
tive precipitation on the scale of 100,000-150,000 km, i.e., over
areas the size of states. A model by Anthes (JAS) similarly sug-
gests that differential surface heating due to alternating plowed
and cropped land will induce circulations and convection.

Cloud modification over the Tusher mountain range (~2000 km2), and
other mountain ranges, is thus undertaken on a scale minuscule
compared to naturally on inadvertently induced phenomena affecting
atmospheric water budgets. Such modification can only be regarded
as a local redistribution of water, albeit such redistribution may
be enormously important to local and downstream uses.

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Cloud modification research is pressing toward breakthroughs in deter-
mining airflow in relation to the delivery of both water substance and seeding
material to the mountain cloud systems, and consequent supercooled liquid
water and cloud water budgets. This is made possible primarily by the

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