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<br />Over the years, the results from cloud physics research and <br />other programs much like our own have been applied to the WKWM <br />Program whenever possible. This helps ensure that the WKWMP remains <br />in a reasonable state-of-the-art mode. We embrace new discoveries <br />and technological development which can be adapted to our specific <br />conditions here and hope our innovations can be used elsewhere. <br /> <br />High numbers of ice nuclei are produced by first vaporizing the <br />liquid seeding agent containing silver iodide. The WKWMP employs a <br />combustion process in which wing generators, filled with a liquid <br />seeding solution containing 2% silver iodide, produce trillions of <br />ice nuclei per gram of silver iodide consumed. The wing generators <br />which are mounted at each wing-tip on all cloud base seeding planes <br />use pressurized air contained in a built-in tank within each <br />generator to force the liquid seeding solution through an aperture <br />to create a fine spray. The spray flows into a combustion chamber <br />where it is vaporized by burning. As the spray burns, very pure <br />particles are formed and exhausted out the tail-end of the generator <br />into cloud base updrafts where the particles are carried aloft by <br />natural action into the cloud's supercooled region. <br /> <br />From 1987 through 1995 the liquid seeding agent formulation has <br />been the same: It contained quantities- of the oxidizers sodium <br />perchlorate and ammonium perchlorate which were added to a silver <br />iodide-ammonium iodide-acetone-water solution resulting in a liquid <br />solution containing 2% silver iodide by weight. However, in 1997 the <br />formulation was changed to contain amounts of silver iodide, sodium <br />iodide, acetone and paradichlorobenzene (C6H4C12). CSU cloud chamber <br />test results indicated total number of ice crystals produced by the <br />new solution at -10C were closely equivalent to the old formulation <br />containing the perchlorates. Also, the particles initially act as <br />hygroscopic condensation nuclei insuring that the formation of vast <br />numbers of water droplets will contain the ice nuclei particles. The <br />ice nuclei initially not trapped in "the water droplets can be <br />captured later by other droplets through random collisions within <br />the cloud. When this happens it is termed "contact nucleation". This <br />entire process of hygroscopic condensation followed by freezing and <br />contact nucleation, forms greater numbers of ice crystals at <br />relatively warmer temperatures within a cloud than by simple contact <br />nucleation. <br /> <br />One important reason to want to use this formulation was due <br />to its clean-burning properties. When this new solution burns, <br />little, if any, residues are produced. Therefore, less generator <br />maintenance is needed over time---of critical important during <br />active operational periods. In the past two seasons using this <br />formulation, wing generator maintenance due to corroded parts has <br />been nil. <br /> <br />In order to obtain the desired effect when seeding clouds, each <br />cloud must be treated within a proper time interval, a "window of <br />opportunity", to produce the optimum ice crystal concentrations in <br /> <br />6 <br />