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<br />002508 <br /> <br />the 1977 HIPLEX season, the contractor collected data on the charac- <br />teristics of cumulus clouds at cloudbase and -5 to -10 .C levels. <br />Data were used in cloud rrodel and cl imatolo9Y studies of the region. <br />Cloud life cycle studies were performed on selected cases to gain <br />physical understanding of cloud and precipitation development, hypoth- <br />esis development, and cloud model verification. Kansas clouds proved <br />to be different from Montana clouds; they are larger, have warmer <br />temperatures, and higher liquid water contents, making them more <br />efficient precipitation producers. The nature of precipitation at <br />cloudbase in Montana is strongly affected by the amount of water in <br />the subcloud layer and the lifted index. The high frequency of ice <br />occurrence in Montana clouds suggests that precipitation is dominated <br />by the ice-phase process. <br /> <br />With the addition of the University of Wyoming computer in 1977, <br />onsite data reduction was possible within hours after a mission. All <br />data are archived on Reclamation's Environmental Data Network. Prior <br />to the 1978 field season, a new Navajo aircraft was instrumented with <br />all previous equipment plus a two-dimensional cloud probe and an ice <br />crystal counter. <br /> <br />CONTRACTOR: South Dakota School of Mines and Technology, <br />Rapid City, South Dakota <br />CONTRACT NO. 5-07-DR-12100 <br />PRINCIPAL INVESTIGATOR: Harold D. Orville <br />PERIOD: July 1,1975 - Continuing <br />FUNDING: FY76 - $47,189 <br />LQ. - $14,940 <br />FY77 - $50,754 <br />FY78 - $83,768 <br /> <br />A two-dimensional, time-dependent cloud model is being used to <br />simulate microphysical and dynamic processes in convective cloud <br />systems and to identify the effects of silver iodide seeding. <br />Results indicate that the potential to augment precipitation is <br />closely related to dispersion of the correct amount of seeding agent <br />into the proper region of the cloud at the appropriate time to obtain <br />optimum effects. Information developed to predict dynamic inter- <br />actions between clouds as a result of seeding are especially impor- <br />tant as HIPLEX progresses toward an exploratory experiment. <br /> <br />The model, originally developed for mountain clouds, was modified to <br />realistically simulate convective clouds of the High Plains region. <br />An important finding in the cloud simulation is that very strong <br />downdrafts and outflows are caused by an evaporating rainshower. <br />High-velocity horizontal winds may cause aircraft to stall when <br />landing. Similar conditions appear every summer in the High Plains. <br /> <br />111-21 <br />