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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />transport processes and allowed simulation of the meteorological and <br />microphysical processes involved in cloud seeding." However, the level-of- <br />evidence issue regarding estimations of winter orographic cloud seeding <br />effectiveness remains a topic of debate. Objective evaluations of non- <br />randomized operational cloud seeding programs continue to be a difficult <br />challenge. <br /> <br />The World Meteorological Organization (WMO) recognized Ihe polential of <br />cloud seeding in favored locations in a statement on the status of weather <br />modification issued in Geneva in June 2001. That statement says under <br />orographic mixed-phase cloud systems: "In OUf present state of knowledge, it is <br />considered that the glaciogenic seeding of clouds formed by air flowing over <br />mountains offers the best prospects for increasing precipitation in an <br />economically. viable manner. These types of clouds attracted great interest in <br />their modification because of their potential in terms of water management, Le. <br />the possibility of storing water in reservoirs or in the snowpack at higher <br />elevations. There is statistical evidence that, under certain conditions, <br />precipitation from supercooled orographic clouds can be increased with existing <br />techniques. Statistical analyses of surface precipitation records from some long <br />term projects indicate that seasonal increases have been realized." Operational <br />cloud seeding programs aimed at enhancing precipitation exist in more than 24 <br />countries (see Figure 1.1). <br /> <br />m::!E!!tD <br />ft (owlCrift wit'" ktlw doed ~In. ,.-oaq.,_ <br /> <br /> <br />, <br />! <br />I <br />, <br /> <br />I <br />~ <br /> <br />Figure 1.1. Countries with active cloud seeding programs <br /> <br />3 <br />