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<br />c) Anticipated dcvelopments and their relevance to Califomia <br /> <br />The foregoing information points to a need tor applied \",'cather modification research that can be <br />integrated into California's operating weather modification programs rapidly and effectively, so <br />that those programs may be optimized. Therefore, anticipated developments in the next few <br />years may be classified as unfolding on t\\'o fronts - applied research and programmatic support <br />for that research. <br /> <br />The most recent weather modilication research effort is Reclamation's Weather Damage <br />Modification Program (WDMP)411. The WDMP \vas begun in late 2002 and was the first <br />Federally-supported research program in over a decade. Although Federal funds were limited <br />(S2M), they were matched by funds from several participating states. Cost leveraging was also <br />achieved by "piggy-backing" the research on operational \veather modification projects already <br />being conducted by those states. The WOMP will conclude in 2006 but most states have already <br />tinished their research, including the orographic seeding states of Utah. Colorado and Nevada. <br />In Utah, a randomized experiment using liquid propane was carried out on the Wasatch <br />Plateau49. Routine targeting of the seeded plume was already assured by prior 1'&0 studies. <br />Seeding dispensers were fully automated, with experimental units (EUs, sc.:eding or <br />placebo) initiated by the detection of SLW cloud with an icing sensor. There was a 25% <br />increase in precipitation of seeded EUs vs. non-seedcd, and seeding generated suflicient ice <br />crystal concentrations to produce at least 0.0 I inch per hour additional precipitation. Given <br />measured SLW frequency. this would yield an estimated 8% inaease in seasonal precipitation. <br />This percentage is close to that given in the AMS policy statement on weather modification30. <br /> <br />The Nevada WDMP was in the Sierra Nevada near the California border. and so its results are <br />highly relevant here. i>.1ajor components were as follows. I) Physical and chemical :mowpack <br />"nalyses from the Walker and Truckcerrahoe Basins using minute amounts of silver. cesium, <br />rubidium. and other chemicals to dctemline and distinguish targeting by seed~d plumes from <br />ground and aircraH sources 50. Results show routine targeting by high-elevation ground <br />generators, and less frequent targeting by aircraft seeding. There was no correlation bch....een <br />snow density and silver content. 2) Mvdelins: .\"llldie.~ - A particle dispersion model integrated <br />with a numerical cloud model was lIsed to predict seeded plume locations. for comparison to the <br />trace chemical analyses and for evaluating seeding generator placementS I. Results show <br />complex and rapidly changing plumes as they move in the rugged terrain of the Sierra Nevada <br />and downwind regions (Figure 5). The modcl also showed contamination in the Tahoe and <br />Nevada Carson target areas from upwind operational seeding projects. Mountain-induced <br />atmospheric gravity waves, \\:hich can dramatically affect T &0, were also predicted. 3) <br />l~rdroloKic mode/inK - A hydrologic model was revised to assess the impact of an assumed 10% <br />precipitation increase in the Walker Rasin. Resulting runotTpercentages varied from 65 to 95% <br />of this added precipitation. depending on soil and vegetation characteristics in the sub-basins. -I) <br />Airl.:raJi microph.niclll measurements - Initial findings show a general inability to document <br />seeding etTects with aircraH. This outcome may be the result of numerous cloud physics aircrall <br />nights over downwind target areas. \\"here evaporation/sublimation of seeding-induced ice <br /> <br />18 <br />