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<br />I <br /> <br />I <br /> <br />A "warm" cloud, 1s a cloud in which temperatures are never <br />below freezing and does not produce ice crystals. This cloud is <br />generally characterized by t~e relatively slow growth of cloud <br />water droplets which eventually attain sufficient size and weight <br />to fall from the cloud. While falling, these comparatively larger <br />drops collect other cloud droplets from the air, scavenging them <br />along their paths. Although this type of cloud may occasionally <br />appear in Western Kansas, it 1s not the kind of cloud that plays a <br />dominant role in the overall production of rainfall here. However, <br />these large warm-rain droplets can be important embryo sources for <br />the production of hail when they are merged into sUb-freezing <br />clouds (not of ~he warm-rain variety) then carried further aloft <br />rapidly by natural cloud updraft action where they freeze and go <br />through a rapid growth process to become sufficiently large enough <br />to reach ground level as hail after falling from the cloud. <br /> <br />I <br /> <br />Of primary importance to Western Kansas 15 the cold cloud. <br />Cold clouds have temperatures below freezing in all or some part of <br />the cloud and produce supercooled water droplets which can initiate <br />the precipitation process. Cold clouds are responsible for most of <br />the significant precipitation occurring in Western Kansas. <br /> <br />I <br /> <br />The prevailing hypothesis under which the hail suppression <br />portion of the WKWM Program operates is that hailstones grow to <br />large sizes because there are too few ice crystals formed naturally <br />in clouds during vigorous thunderstorm development thereby allowing <br />abundant supercooled water to collect upon relatively fewer numbers <br />of ice particles or other hail embryos. Subsequently, those <br />particles are able to grow into hailstones frequently too large to <br />mel t before reaching ground. Therefore, we theorize the need to <br />increase ice crystal concentrations within the ice crystal- <br />deficient clouds so that hailstones large enough to reach those <br />sizes capable of damaging crops and property cannot develop. There <br />are other theories about bail development and movement within a <br />cloud and it i$ likely that hail doesn't always form exactly the <br />same way, every time, in every cloud. It. is interesting to note, <br />however, that since hail suppression cloud seeding began, long-term <br />cloud seeding programs around the world, using .the same hypothesis <br />as the WKWK Program, usually have shown varying degrees of reduced <br />crop-hail damage at high levels af ~~atistical confidence. <br /> <br />Earlier it was mentioned that silver iodide and dry ice remain <br />the primary materials used in treating clouds. The WKWM Program <br />currently uses both. In the first case an aircraft delivers silver <br />iodide into updrafts at cloud bases. In the second case an aircraft <br />delivers dry ice into growing clouds at atmospheric levels, usually <br />araund 20,000 feet in mid-summer Kansas. Over the years, results <br />from weather modification programs, worldwide, and cloud physics <br />research has been applied to the WKWM Program to maintain a <br />reasonable state of the art capability. <br /> <br />I <br />I <br /> <br />7 <br />