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1.0 OVERVIEW <br /> In 2003 the Texas Department of Licensing & Regulation (TDLR) was awarded a grant from the U. S. <br />Bureau of Reclamation to participate in a collaborative effort known as the Weather Damage Modification <br />SP <br />Program (WDMP). The research, which was to be supported by the grant and known as the outhern lains <br />ECTRASPECTRA <br />xperiment in loud-seeding of hunderstorms for ainugmentation (), was to evaluate the <br />physical mechanisms in the atmosphere, particularly within convective cloud towers, to identify and administer <br />appropriate cloud seeding materials that would lead to the reduction of damage, and loss, due to drought and <br />hail. <br /> The original plan called for the research to be conducted in two phases in the Texas-Oklahoma portion <br />of the southern U. S. Great Plains region during the spring and summer of 2004. Unforeseen delays in the bid <br />solicitation process allowed only the initial phase of the research to be accomplished during the late summer of <br />2004. This effort was called SPECTRA I. SPECTRA II was completed during May and June 2005 and is the <br />focus of this Final Report. <br />2.0A RECENT HISTORY OF CLOUD SEEDING RESEARCH IN TEXAS <br />Since 1997 the State of Texas, through the TDLR and other predecessor state agencies (The Texas <br />Natural Resource Conservation Commission and the Texas Department of Agriculture), has assisted local <br />political subdivisions (such as water conservation districts, aquifer authorities, and county commissions) with <br />the design, implementation, and maintenance of cloud-seeding programs for rainfall enhancement. The State, <br />through grant agreements with these political entities, has covered up to 50 percent of the cost to conduct cloud <br />seeding operations. In all, over the past eight years, the State has dispensed nearly $14 million to weather <br />modification projects in West and South Texas. At least an equivalent amount of ad valorem tax monies, <br />raised by the water districts and counties involved in the operations, has been expended to pay for the projects. <br />Rain enhancement operations are now conducted, at least during the growing season (April-October), <br />over roughly 37 million acres of Texas. These projects were established as a consequence of research in <br />weather modification technologies, much of it conducted in Texas over the past three decades, sponsored <br />initially by the U.S. Bureau of Reclamation, then by the National Oceanic and Atmospheric Administration <br />(NOAA) and most recently by the Bureau of Reclamation. Until recently, the bulk of this research focused on <br />the use of glaciogenic materials (flares consisting of the ice-producing compound, silver iodide, AgI) to <br />promote cloud growth, and the resulting additional rain volume released by the cloud tower in its mature stage. <br />Thus, it is not surprising that, heretofore, cloud seeding in Texas has targeted those cloud towers having <br />0 <br />< <br />an abundance of supercooled water in that portion of the tower where the temperature is -4C. But what <br />about those cloud conditions, often prevalent in semi-arid regions of the state in which there is a paucity of <br />supercooled water? Interest in using hygroscopicmaterials has flourished in Texas as evidence has accrued in <br />other parts of the world that seeding with salt particles has promoted cloud growth and rainfall in instances in <br />which glaciogenic seeding would have been counterproductive. <br />2.1Completion of SPECTRA I Research Work <br />Among the principal objectives of SPECTRA has been the identification of types, and frequency of <br />occurrence, of cloud condensation nuclei (CCN) within and in the vicinity of growing convective cloud towers. <br />12 <br />