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<br />II. Proposed Action and Alternatives <br /> <br />A. Background information <br /> <br />The study area would be the winter precipitation accumulation zone of <br />Grand Mesa, above 9000 feet. Figures 1 and 2 show the location of the <br />study area. Grand Mesa was selected because its elevation, relatively <br />flat terrain, and easy access ~ake it a good outdoor laboratory for <br />these studies. Because of its location and elevation it receives a <br />variety of winter storms including northwesterly, westerly, and south- <br />westerly events. It is centrally located between two general storm <br />types that affect the southern and northern mountain ranges of the Upper <br />Colorado River Basin, which enhances the potential data collection and <br />evaluation opportunities to be expected. The upwind terrain is sU1table <br />for installation of groundbased silver iodide (AgI) seeding generators <br />for most wind directions. Because of its accessibility, a variety of <br />equipment including aircraft, radar, radiometers, satellite-reporting <br />data-collection platforms, and mobile ground units can be operated for <br />concurrent data acquisition. Because of its relative flatness, explora- <br />tory cloud physics aircraft flights can be conducted in clouds at low <br />altitudes, within 1,000 feet of the highest terrain. <br /> <br />Equipment for the climatological studies presently being conducted on <br />Grand Mesa is housed in trailer facilities (see figure 3) or consists <br />of precipitation gauges in small forest clearings, all installed <br />under Forest Service permits. <br /> <br />~ <br /> <br />~ <br /> <br />For the climatological studies, several important parameters are <br />measured throughout each storm event during as many storms as prac- <br />tical through the winter season (early November to late March), <br />including precipitation (amount, intensity, and duration), liquid <br />water content of the clouds, air temperature, wind speed and direc- <br />tion, atmospheric pressure, and dewpoint temperature. A continuous <br />record of these parameters will permit investigation of several <br />important problems, including: <br /> <br />1. How frequently do clouds occur <br />2. When they do, how frequently is liquid water present and in <br />what amounts <br />3. Is liquid water more frequent with shallow storms (low cloud <br />tops) <br />4. How often is it cold enough for significant AgI nucleation <br />when liquid water is present <br />5. How often and where does the -130 to -17 oC rapid growth range <br />occur <br />6. Is liquid water content related to wind speed and direction <br />7. What wind speeds, direction, and direction fluctuations accom- <br />pany the apparently seedable situations (related to generator pla- <br />cement and spacing) <br /> <br />t <br /> <br />y <br /> <br />2 <br />