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MS Defense

Department of Atmospheric Science

Tues., Apr. 30, 3:10 pm, EN6085

Climatology of Favorable Conditions for Ground Based Cloud Seeding In the Wind River Range

Thomas Mazzetti

University of Wyoming

Abstract

The mountainous regions in the world provide much water, as runoff, to lower basin regions for human and environmental consumption. With the inevitable change in climate, human population and behavior, it is important to plan for the future of water resources. Glaciogenic silver-iodide cloud seeding has been shown to be a plausible way to convert supercooled liquid cloud water into ice. Ice can grow faster than liquid because of greater supersaturation with respect to ice rather than liquid; which may result in more precipitation. The main unknown in the glaciogenic seeding of clouds remains the supercooled liquid water content, therefore it remains unclear under what conditions cloud seeding is most effective for increasing snowpack and water storage in the mountains, and how common those conditions typically are in a winter season.

The goal of this study is to quantitatively estimate impact, and to determine the most favorable conditions for ground-based cloud seeding. This work focuses on the Wind River Range (WRR) in Wyoming because it has had a continuous cold-season ground-based seeding operation from Fall 2007 to present. This range, the headwaters for several basins as part of the continental divide, is a relative steep and linear mountain range.

This study has two steps. The first step (the MSc thesis) is to better understand the climatology of conditions believed to be suitable for snowfall enhancement by cloud seeding in the WRR; for this, a high-resolution WRF regional climate simulation is used. The logical second step (reserved for the PhD) is to quantitatively estimate seeding impact, and to determine the most favorable conditions and most effective method for cloud seeding over the WRR. For this, higher-resolution simulations with a cloud seeding module are done, to quantify the seeding impact on surface precipitation.

Here, first step is the focus. Cold-season composites of upstream thermodynamic and wind profiles over the WRR, and spatial, seasonal and diurnal variability of these conditions are examined. It was shown that there is about 9.25 and 1.47 days per year of time that the conditions are favorable for ground-based seeding (temperature range, presence of super cooled liquid water, flow pattern, and static stability). Also, seedability varies greatly with the time of day, season, and flow direction (easterly or westerly). This study helps outline the rationale behind favorable conditions for ground based glaciogenic cloud seeding. The approach used here can be applied to many mountain ranges around the world to determine the efficacy of cloud seeding to increase water resources.

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Phone: (307)766-3245

Email: geerts@uwyo.edu

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