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Last modified
7/28/2009 2:27:55 PM
Creation date
10/1/2006 2:13:12 PM
Metadata
Fields
Template:
Weather Modification
Applicant
Arlin Super, William Woodley, John McPartland
Sponsor Name
Denver Water
Project Name
Cloud Seeding Analysis
Title
Silver-In-Snow Evaluation of Cloud Seeding Effectiveness for Snow Pack Ehancement in Colorado During the 2002/03 Season
Prepared For
Denver Water
Prepared By
Super, Woodley, Heimbach
Date
6/16/2003
State
CO
Weather Modification - Doc Type
Scientific Study
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<br />'" <br /> <br />There are not many good examples of demonstrated well-targeted seeding programs, <br />together with available seasonal silver-in-snow concentrations. Therefore, it is difficult to be very <br />specific about what silver concentrations should be anticipated in the DWB seeding project if <br />routine targeting was achieved. But the observations presented by Chai et al. (1993), Warburton et <br />al. (1995a), Warburton et al. (l995b) and Stone (1997) suggest that proper targeting should provide <br />at least about 10 ppt seeding silver, wid sometimes 50-115 ppt, for short-term samples. The BRE, <br />the only project with demonstrated routine targeting from aircraft and mountain-top observations <br />of AgI, produced seasonal samples in the range 30-100 ppt, with a median of 46 ppt. Less than half <br />of all storms were seeded in this randomized experiment where statistical analyses strongly <br />suggested that operational seeding could produce at least 15 percent seasonal snowfall increases. It <br />seems reasonable to expect that an operational project which achieves proper targeting for, say, 1/4 <br />to 1/2 of all storms should result in greater than 10 ppt silver-in-snow concentrations. Seasonal <br />samples with less than 10 ppt silver can be interpreted as evidence of poor targeting with little <br />resulting snowfall augmentation. A routinely targeted operational project should produce at least <br />the 30-100 ppt values observed in the randomized BRE. <br /> <br />3.0 SILVER-IN-SNOW OBSERVATIONS FROM THE DWB 2002/03 SEEDING <br />PROGRAM <br /> <br />3.1 Selection of Snow Sampling Sites <br /> <br />Ten locations were chosen in the intended target area of the DWB seeding project for <br />sampling the seasonal snowpack and analyzing silver contents. These sites were chosen to <br />provide good spatial distribution over the target area, and with elevations and local exposures <br />that would minimize snowmelt in the mid-March to mid-April timeframe. Early snowmelt could <br />confuse interpretation of the silver-in-snow concentration results. <br /> <br />For convenience, existing manual snow courses and SNOTEL pressure pillow observing <br />sites were used as references in site selection. Snow samples were collected in the vicinity of <br />each snow course or SNOTEL site, as close as was reasonable within travel constraints. All snow <br />samples were collected within 0.6 mile of the reference snow courses or pillows with the <br />exceptions of a ].2 mile difference for the Michigan Creek target site and 3.1 mile difference for <br />the Rabbit Ears Pass control site. Budget limitations precluded helicopter or snowmobile travel. <br />Most sampling was done by Mr. Jack McPartland snowshoeing from available highway vehicle <br />parking places to as near the reference site as practical within about an hour's travel. Vail and <br />Copper Mountain Ski Areas generously provided ski lift access to sampling locations. <br /> <br />Mr. Larry Hjermstad, President of Western Weather, was invited by the DWB to provide <br />a selection of ten stations which he believed were well targeted by his company's operational <br />seeding. Using the Western Weather-suggested stations wherever they appeared reasonable <br />allowed the seeding contractor to take his "best shot" at estimating where seeding was most likely <br />to be effective. The snow sampling locations may not be "typical," but should represent locations <br />more likely to be seeded than the overall target. It was decided to take this approach because of <br />the difficulties past projects have had in demonstrating proper targeting. If the results showed <br /> <br />14 <br /> <br />
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