Weather Mod Critical Issues Report

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. I I I I I I I I I I I I I I I I I I I conclusions presented in previous reviews, rather than retreat to the position that it is premature to conduct operational projects. 3.2.5 Primary concerns in winter orographic programs (a) Transport and Dispersion: One of the most significant uncertainties in larger scale seeding projects is the transport and dispersion ofthc seeding aerosols across the project areas, Results from several studies have revealed that most of the precipitation falling in the targets during seeded periods has not been impacted by the seeding process, assuming that the absence of the seeding chemical in the snowfall can be used for making such a deduction. New fully automated ground-based generators can be located in often not very accessible locations in the higher terrain of mountains thus reducing the problems of getting seeding materials into targets. Trace gases can also be used to track the seeding material through the target and if it occurs through the control areas. (b) Remote Sensing: Although the wind profiler, the dual-channel microwave radiometer and the polarimetric radar and other short wavelength radars have found substantial use in specific snowpack programs prior to 1995, it is unfortunate that very few of these devices are available to the scientific or weather modification community outside of government agencies. There is a great need for resources and actual construction of such apparatus for new scientific research efforts. (c) Statistical Analysis Methods: Because of the opportunity to shift the design of larger-scale seeding experiments to the use of physical and chemical assessment methods and to continue to satisfy the requirement of unbiased randomization, there is now a special need for new statistical approaches that are coupled with physical observations enabling comparisons to be made between those portions of the snowpack which have been impacted by the seeding during a seeding period and those which have not. For example, can snow samples that contain no seeding materials be considered as a "no-seed" comparison set? (d) Trace Chemical Facilities: It will be essential to ensure that adequate trace chemical laboratories are available for analyzing the snowfall for silver, indium, cesium and other tracer materials used in these snowpack augmentation studies. A few such laboratories do exist in the V.S, most of which have not been involved in weather modification. (e) Environmental Impacts of Cloud Seeding Programs: Nearly all orographic weather modification programs in the western V,S. involve public lands, All agencies both governmental and private that engage in these weather modification programs are confronted from time to time by concerned citizens and environmental groups with questions about the environmental impacts of weather modification and the chemicals used in these programs. In cases where seeding aerosol generators are to be located on public lands, the land manager (e.g" V .S. F orest Service) is required to issue an environmental assessment and negative declaration prior to issuing special use permits for generator sites, Public agencies such as municipal utility districts, and state water 20