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<br />2 <br /> <br />~ <br /> <br />objective is to carefully observe the cloud and surrounding atmosphere <br /> <br />furnishing physical descriptors for use in model development and eva1u- <br /> <br />. <br /> <br />ating the potential application of cloud modification technology. This <br /> <br />study was designed as one of the phases of the design study of the <br /> <br />Bureau of Reclamation's pilot seeding project (Grant, et a1., 1969). <br /> <br />A critical problem in any study of the hydrometeorology in moun- <br /> <br />tainous areas is obtaining accurate estimates of precipitation. Such <br /> <br />estimates are critical in the evaluation of seeding results and are <br /> <br />complicated by the fact that precipitation varies widely with altitude <br /> <br />and local topography (e.g., Hjermstad, 1970). The direct measurement <br /> <br />of precipitation over mountainous terrain has been accomplished for <br /> <br />rather localized experimental areas and even in these instances the <br /> <br />~ <br /> <br />sampling sites were located for their accessability. To expand such <br /> <br />~ <br />~ <br /> <br />special networks to include any location is prohibitive from both cost <br /> <br />. <br /> <br />and safety viewpoints. Alternative techniques of measuring precipi- <br /> <br />tation yield must be developed. This paper further describes the ap- <br /> <br />plication of one such technique, the atmospheric water balance. <br /> <br />Another problem that arises in the study of modification of oro- <br /> <br />graphic clouds is the observation of individual cloud system efficiency <br /> <br />in producing precipitation. Evidence to date is largely derived from <br /> <br />indirect relationships, for example, ice nuclei counts, that are mean- <br /> <br />ingful only in statistical summary; therefore, individual clouds can- <br /> <br />~ <br /> <br />not be directly accessed. In this paper the study of the atmospheric <br /> <br />water budget is used to evaluate the efficiency of orographic clouds. <br /> <br />. <br /> <br />To date there have been several attempts to develop a model of <br /> <br />the airflow over a mountain ridge and the resulting precipitation <br /> <br />(e.g., Myers, 1962; Elliott and Hovind, 1964; Willis, 1970), Lacking <br />