Cloud Seeding in the Walker River Basin Arlen Huggins Desert Research Institute

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Cloud Seeding in the Walker River BasinArlen
HugginsDesert Research Institute

• Scientific basis for wintertime cloud seeding
• Determining the potential for increased snowfall
• Seeding methods and materials
• Detecting the impact of cloud seeding
• Current activities in the Walker Basin
• Future directions

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Cloud Seeding A Brief History

• Cold Box Experiments 1940s
• Operational Projects 1950s to present
• Research Projects
• Field Studies (1960s - 1990s)
• Statistical Experiments (1960s and 1970s)
• Proof of Concept Experiments (1980s-1990s)
• New Evaluation Techniques (1980s - ?)

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Current Wintertime Seeding Projects
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Concepts for Cold Cloud Seeding

• Winter clouds contain some water that has not
  been converted to ice crystals and snow
• Amount of supercooled liquid determines seeding
  potential
• Ice forming particles (nuclei) required to
  produce ice
• Natural ice nuclei are less numerous at warmer
  temperatures
• Artificial seeding either adds more ice nuclei or
  reduces the temperature so ice can form
• Seeded ice crystals grow and fall as snow

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Sizes of Cloud Water and Ice Particles
1 mm
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The Potential for Cloud Seeding

• Storm Frequency and Duration
• The Amount of Supercooled Liquid Water in a Storm
• Targeting Considerations

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Seasonal Precipitation
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Supercooled Liquid WaterRemotely Sensed
Microwave Radiometer Measures Cloud Liquid
Depth and Water Vapor Depth
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Supercooled Liquid Water Integrated Effect
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Conceptual Model for Cloud Seeding
Seeding Generator
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Modeling to Evaluate Generator LocationsSeeding
Simulation Time 1700 2/14/94
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Modeling Plume after 30 minutes
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Modeling Plume after 1.5 hours
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Modeling Plume after 7 hours
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Aircraft Cloud Seeding
AgI Flares in Aircraft Flare Rack
AgI Solution Burners
Nighttime Flare Test
Dry Ice from an Aircraft Hopper
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Ground-based Cloud Seeding
DRI Remotely-controlled cloud seeding generators.
Left Mobile Unit Above Semi-permanent Unit
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Generator Ice Crystal Production
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Detecting the Effects of Cloud Seeding1.
Statistical Methods
California 1969 AgI Seeding 0.1 mm/h Colorado
1971 AgI Seeding 0.1-0.7 mm/h Montana
1986 AgI Seeding 0.3 mm/h
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Detecting the Effects of Cloud Seeding2. Direct
Observation
Washington 1975 AgI/CO2 0.15 - 0.9 mm/h Nevada
1987 CO2 0.1 - 0.6 mm/h Montana
1988 AgI 0.05 - 0.2 mm/h Colorado
1988 AgI 0.1 mm/h California
1988 AgI/CO2 0.3 - 1.0 mm/h Utah
1994 AgI 0.5 - 1.5 mm/h
0.25 mm/h 0.01 in/hr Over 35 sq. miles Seeding
effect 18.7 acre-feet/hour For 8 storm hours
149.6 acre-feet For 20 storms 2992 acre-feet
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Seeding Effects Detection Methods
Aircraft or Vehicle-mounted Particle Probes
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Seeding Effects Detection Methods
Short-wavelength Radar
Snow profiling for chemical analysis
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Seeding Effects Some Results
Seeded Period
A 1-hour AgI Seeding Experiment in Utah
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Seeding Effects The Aerosol Plume
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Seeding Effects A Radar Plume
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Seeding Effects Precipitation Data
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Walker Basin Seeding Program
6 ground-based generators for 2001-02 8-9
generators by 2002-03 Aircraft Seeding over
Sierra Nevada
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Future Directions

• Detailed Sub-basin Evaluation of Seeding
  Opportunities and Impacts
• SLW climatology from radiometer data
• Snow Core and Chemical Analysis of Snowpack
• Modeling Study to Evaluate Future Ground
  Generator Locations
• Emphasis on targeting high SLW regions
• Generator network expansion
• Observation/Modeling Study to Evaluate Runoff
  Impacts