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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />- lV - <br /> <br />the possible effects of artificial seeding on precipitation <br /> <br />are given. <br /> <br />In Section 6 four case studies are described in which <br /> <br />clouds were seeded with silver iodide from the aircraft for <br /> <br />short periods of time ln an attempt to modify their structure <br /> <br /> <br />and change the nature of the precipitation downwind over a <br /> <br /> <br />small predetermined area. In two of the cases effects <br /> <br /> <br />attributable to the artificial seeding were detected at <br /> <br /> <br />ground level in the target area, in the third case the <br /> <br /> <br />clouds appeared to be completely glaciated by the seeding, <br /> <br /> <br />and in the fourth case no marked effects on precipitation <br /> <br /> <br />were detected in the target area but at one of the ground <br /> <br /> <br />stations there was a significant increase in the concentra- <br /> <br />tions of freezing nuclei following the artificial seeding. <br /> <br />A small CW Doppler radar was built and operated in the <br /> <br />Cascade Project during 1970-71. This radar is described in <br /> <br />Section 7 and some of the data obtained are presented. <br /> <br />In an Appendix to the report, the characteristics of a <br /> <br />suitable radar for general investigations of precipitation <br />in the Pacific Northwest of the United States are described. <br />Because of the nature of the precipitation and the require- <br />ment of high spatial resolution, it is suggested that a <br />5-cm radar with a beamwidth of about 0-50 is the best choice. <br />Such a radar should be capable of providing quantitative <br />information on radar reflectivity and could be used for <br />synoptic, hydrological, cloud physics and weather modification <br /> <br />investigations. <br /> <br />