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<br />000176 <br /> <br />changes which occur in the clouds and on the ground. Fully instru- <br />mented cloud physics aircraft will be required, as will surface <br />monitors such as radars, microwave radiometers, icing rate meters, <br />snowfall rate sensors, and other specialized equipment. Mobile <br />facilities will be transported throughout the subbasins to conduct this <br />work. <br /> <br />C. Extra-Area Effects <br /> <br />The need to address the possible existence of effects beyond the target area <br />and their consequences is explicitly recognized as an important component <br />of the CREST Program. <br /> <br />The major extra-area effects issue concerns whether seeding increases or <br />decreases snowfall in the regions immediately downwind of the areas <br />targeted for precipitation augmentation. The region of concern encompasses <br />the lee slope of the mountain ranges targeted for cloud seeding and the <br />crests of the next major ranges downwind. If effects cannot be found <br />there, a search for them at a greater distance is likely to be fruitless. <br /> <br />A second important issue is whether the seeding may affect the development <br />of storm systems as they pass beyond the targets and move into the lee of <br />the Rockies, a region well known to meteorologists as the birthplace of <br />new storms and a place where weak storms are likely to find new strength. <br />If seeding were to affect the subsequent history of the storm, the results <br />would be of significant importance for any program of precipitation <br />management. The likelihood, though considered small, cannot be dismissed. <br /> <br />Any effect that cloud seeding has on precipitation and storm development <br />beyond the target area will affect the natural environment and, more <br />immediately, the activities of people in the region thus influenced. <br /> <br />The study of these impacts will continue to be addressed along with <br />environmental requirements for acceptable precipitation management. The <br />specific role of the extra-area effects program element for CREST will be <br />to supply the basic data regarding precipitation in the downwind areas of <br />the CREST targets. <br /> <br />Snow gages, like those used in the primary target areas, will be placed on <br />the lee slopes of the target ranges and in the heavy snowbelts of immedi- <br />ate downwind ranges. Density of placement will be reduced to about one- <br />fifth that in the primary targets. Initially, maximum use will be made of <br />ski areas and other manned high-altitude locations as gage sites. Later, <br />remote gages will be installed to complete the network. Observations from <br />these gages will become part of the project data bank, available for <br />analysis capable of detecting precipitation changes comparable to those <br />analyzed in the primary target areas. In addition, analyses will be <br />conducted to see if precipitation that could be associated with seeding in <br />the target area can be identified through the presence of seeding agents <br />in the snow. <br /> <br />The farther away one looks for possible effects of cloud seeding, the <br />more the direct effect of the seeding becomes confused with strengthening, <br />weakening, or other changes in the structure of the storm itself. <br /> <br />35 <br />