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<br />of others, with other processes being added one by one. The field observation <br />component will complement and test findings from the modeling and laboratory <br />work, provide feedback and guidance for those components, and examine in situ <br />the integrated activi ty and interaction of the ice processes as functions of <br />actual cloud structures. <br /> <br />A 10-year program is planned. Close cooperation with universities and <br />private research organizations is expected. Laboratory and modeling work will <br />proceed throughout the 10-year period. Field work will be scheduled on an <br />irregular basis to correspond to cloud climatologies and to allow time for <br />substantial field data analysis and inputs of laboratory and modeling results <br />between operations. <br /> <br />Many new techniques for probing the microphysical structure of clouds <br />have become available only recently. Several of these techniques employ <br />optical and microwave remote sensing devices which need to be combined into a <br />coherent measuring and data processing system. Hence the first-year field <br />study, now proposed for January-March 1982, is designed to be a systems test <br />of these new techniques. It will address program objectives for one type of <br />physically suitable cloud system, demonstrate capabilities and limitations of <br />observational instrumentation, and provide a coherent data set for analysis. <br /> <br />For convenience and because of their advantages as an outdoor laboratory, <br />the clouds associated with the winter upslope type of storm that affects the <br />plains and foothills along the eastern slope of the Colorado Rocky Mountains <br />will be the objective of the proposed first-year investigations. These storms <br />occur bet".o1een November and April wi th an average frequency of about 10 events <br />per season. An event may last more than one day. Temperatures at the heights <br />where these upslope clouds end are commonly far warmer than-20oC, often -lOoC <br />or even warmer. These upslope storms are often remarkably shallow (600- <br />900 m), and yet periods of intense precipitation are common. <br /> <br />The field effort will focus on determining of two encompassing factors <br />that are believed to control cloud modification potential: <br /> <br />o The quantitative spatial and temporal distribution of liquid water <br />in relation to cloud circulations on scales of 100 m to 100 km. <br /> <br />o The corresponding space-time evolution of ice particles, in terms of <br />concentration, particle type, and the accompanying physical and <br />dynamical conditions, especially in early stages of cloud <br />development. <br /> <br />The laboratory eKperimentation will provide fundamental, interactive <br />support to the field studies throughout the program. Investigations of ice <br />particle multiplication processes and "anomalous" warm temperature nucleation <br />should receive high priority beginning the first year. Other studies <br />particularly relevent to upslope storms will also be conducted. Dynamic and <br />static cloud chambers, electron microscopes, and other laboratory apparatus <br />will be employed as appropriate. <br /> <br />- 38 - <br />