The Feasibility of Operational Cloud Seeding in the North Platte River Basin Headwaters to increase Mountain Snowfall

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The proposed project must confront the evaluation design issue in the program design phase. The program design phase must also confront that previous studies suggest that the window of opportunity for obtaining precipitation increases from cloud seeding is narrower than previously conceived (Cotton and Pielke, 1995). Furthermore, it is apparent in previous studies that successful cloud seeding procedures for one area may be failures in another site. These results support that each area requires separate study and the development of an individualized cloud seeding design. A major concern for the design phase is the diverse terrain of the Headwaters Region and that cloud seeding effects must be targeted for the lee side for portions of the western barrier. The proposed project for the Headwaters Region must include a well - conceived design phase aimed at developing, among several components, an operational seeding plan for the specifics of the area. Figure 1.1 presents a layout of the main high elevation areas of the Headwaters Region. The Park Range in northern Colorado extends into southern Wyoming where the barrier is called the Sierra Madre. The entire western barrier is sometimes referred to as the Park Range. The Medicine Bow Mountains on the east side of the Headwaters Region also extend from northern Colorado into southern Wyoming. Lengths of the higher elevation portions of the two primary barriers are about 65 mi for the Park Range north of Rabbit Ears Pass, and 70 mi for the Medicine Bow barrier from Cameron Pass on the south. Runoff from more southerly portions does not drain into the North Platte River. The figure shows large wilderness, areas in the west and east barriers that will challenge the operational seeding design. The proposed project must use the latest tools of measurement of field variables such as winds and cloud liquid water, and numerical simulation tools including three - dimensional cloud models that can assist and expedite the design of the cloud seeding component. Because of improvements in computers and cloud model development and testing the past couple of decades, computer models are available to assist in the project design, conduct and evaluation. For example, the Colorado State University cloud model known as the Regional Atmospheric Modeling System (RAMS) has had some application to differing winter storms over the Headwaters Region, at the high resolution of three - kilometer grid point spread. High resolution simulation is needed to provide more information on parameters of orographic clouds that are important to cloud seeding. Some results of recent cloud simulations with RAMS will be given later in this report. I 1.2. Program General Plan I The proposed project is aimed at providing additional snowfall in the Headwaters Region. The project plan will consist of two principal components: (1) an operational phase with proper evaluation capable of determining cloud seeding effects on precipitation, (2) a cloud seeding design phase that consists of ' studies aimed at determining and testing how to best seed winter clouds in the headwaters region and what information must be collected in the operational phase for proper evaluation and environmental awareness. Because each geographical area presents different meteorological and terrain conditions than others studied, the project plan must include developing a cloud climatology and response to the highly varying terrain of the Headwaters Region. The design phase must establish what measurements and equipment are appropriate for the operational phase. Supplementary studies may be conducted by partner agencies as part of the project design phase and/or the operational seeding phase. These studies can contribute additional information of value to the