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<br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />. <br />. <br />. <br /> <br />new software was written to define and track <br />seeded echo areas and match them objectively <br />With comparable non-seeded echo areas. The <br />method builds on their research studies and <br />publications dealing with the effect of seeding in <br />randomized seeding programs in Florida. Texas <br />and Thailand. The Woodley and Rosenfeld <br />methodology has been published in Woodley. <br />W.L and D. Rosenfeld (2004). <br /> <br />Potential statistical <br />uncertainties <br /> <br />evaluation <br /> <br />The evaluation of randomized cloud seeding <br />experiments in Texas. South Africa. Mexico. and <br />Thailand was based on estimates of rainfall from <br />radar. These results using radar estimated <br />rainfall have been published in peer reviewed <br />journals. specifically those periodicals <br />copyrighted by the American Meteorological <br />Society (AMS). Silverman (2003) referring to the <br />South Africa, Mexico. and Thailand experiments. <br />comments that in his opinion. '"the statistical <br />results ... are quite remarkable. especially when <br />one considers that the experiments are quite <br />diverse in geographical location, in <br />meteorological setting, in design. and in <br />experimental and evaluation procedures. <br /> <br />One of the few or the only, peer reviewed <br />published randomized cloud seeding <br />experiments using estimation of rainfall from rain <br />gauges was conducted over an extended period <br />of time in India during the summer monsoon <br />seasons of 1957 to 1966. The evaluation of the <br />experiment was based on the 24-hour rainfall <br />measured by 90 rain gauges. Cotton (1982) <br />quoted in Silverman (2003) stated. While the <br />results of the Indian experiments must still be <br />viewed as ambiguous, they cannot be thrown out <br />as invalid.M <br /> <br />Selecting an appropriate control area <br /> <br />Perhaps the most fundamental requirement in <br />the beginning of any statistical evaluation is the <br />selection of a Mcontrol area" for the cloud seeding <br />"target area". <br /> <br />. <br />I <br />I <br />I <br />I <br /> <br />The target area is the area in which the objective <br />is to increase the precipitation. The equipment <br />and instrumentation deployed to increase rain in <br />the target area may be positioned to gather data <br /> <br />or treat cloud systems over a somewhat larger <br />area. This will allow treatment of systems <br />approaching the target from a variety of <br />directions and in varying meteorological <br />conditions. <br /> <br />The objective of selecting a control area is to <br />observe unseeded cloud systems near the target <br />area. The control area is the geographical <br />boundary beyond the target area from where <br />data is collected and analyzed_ The total area, <br />geography, climatology, and use of the control <br />area should be as similar 10 the target area as <br />possible (ASCE. 2004). <br /> <br />One has to be very cautious when selecting a <br />control area for the seeded target. For example, <br />in the Southern Ogallala target. most of the storm <br />motion has a northeasterly direction. As can be <br />observed in figure 16. if the control area is <br />selected to be on the northeast side of the target. <br />the control area will be downwind of the <br />predominant storm motion. It would be <br />erroneous, therefore. to select this area as a <br />control, since seeded clouds will continue to rain <br />downwind. If this control area to the east and <br />northeast is used in the analysis. the result of a <br />seeded vs. control target area would culminate in <br />an inconclusive or negative affect of seeding. It is <br />very fundamental that any seeded area vs. <br />control area analysis includes a rain gauge <br />climatology and a storm direction climatology. <br /> <br /> <br /> <br />, <br /> <br />? <br /> <br />I <br /> <br />;; <br />? <br /> <br />Figure 16: Storm tracking climatology for May <br />2003 in the Southern Ogallala target. The red <br />shaded box shows an area that could be used as <br />a control area. but it is not suitable since it is <br />downwind of the seeded clouds. <br /> <br />28 <br />