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<br />climatological aspects of the High Plains cloud systems are different. <br />A climatological study of these cloud systems is basic to an in- <br />vestigation of the feasibility of augmenting their natural preC'ipitation. <br />Information required includes synoptic data on the development of up- <br /> <br />slope storms, as well as their areal coverage, duration, movement, <br /> <br />and frequency of occurrence. Characteristics of the clouds, such as <br />cloud thicknesses, lapse rate, cloud top temperatures, and wind speeds <br />and directions, are also related to the natural efficiency of precipi- <br />tation from these cloud systems. <br />In this report, a model of the seedability, or potential for <br />artificial release of precipitation from these shallow cloud systems, <br />is developed. Twice-daily rawinsonde data for each station in the <br />High Plains are then compared with the. model, and soundings meeting the <br />model criteria are used in the climatology. Results of an investigation <br />into the climatology of seedable orographic cloud systems are presented. <br /> <br />2. A MODEL OF SEEDING OPPORTUNITY RECOGNITION <br /> <br />'1' <br />A model is developed that describes the vertical structure of a <br /> <br />-~,i <br /> <br />theoretically seedable supercooled cloud layer. Figure 1 shows speci- <br />fications of the model. <br /> <br />Individual rawinsonde soundings are compared with the vertical <br />structure specified in the model. Soundings satisfying the model <br />criteria are considered to indicate the presence of a seedable cloud <br />layer. Model criteria include: <br />1. A moist layer with relative humidity ~ 85 percent. This <br />layer defines the vertical extent of the cloud deck. <br /> <br />3 <br /> <br />!' <br />