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<br />After the eighth penetration the crew on the research aircraft decided to <br /> <br />climb to try and again interce?~ the line of ice nuclei. As the aircraft <br /> <br />climbed higher in ~he cloud na~ural particle concentrations decreased. Now <br /> <br />definite increases in concentrat~on ~ere observed simultaneous with seedline <br /> <br />penetrations at 55 and 61 rroin. These penetrations were at temperatures < <br /> <br />-80G. <br /> <br />Because the aircraft had cliffibed into higher winds its tracking <br /> <br />information was invalid; however, strong signals on the ice nucleus counter <br /> <br />confirmed seedline penetration for the last 5 passes, 64-92 min. <br /> <br />Increases in <br /> <br />particle concentration were also obser~ed during these five penetrations, Fig. <br /> <br />4, at temperatures between -9 and -12.60G. For these penetrations the <br /> <br />advection speed of the seedline increased from 18 to 20 m s-l. Given the age <br /> <br />of the seedline and the width of the ice crystal plumes the dispersion rate <br /> <br />was calculated to be 1.3 m s-~. <br /> <br />Inages indicated that the particles in the <br /> <br />seedline were primarily graupel and plates, while outside of the seeded pluree <br /> <br />the crystals were<branched crystals and aggregates. After the penetration at <br /> <br />92 min the research aircraft returned to base. The seedline was now nearing <br /> <br />the crest and the dow~wind edge of cloud. <br /> <br />The seeding material was released in the upwind edge of an echoing <br /> <br />orographic cloud with reflectivities of 15-20 dBZ. Although there was evidence <br /> <br />of ice generation near 5 km, and s~bsequent enhancement of reflectivity as the <br /> <br />particles fell throug~ the cloud, the echoing region was generally below 5 km. <br /> <br />The seedline remained with this same level of background echo throughout the <br /> <br />92 min of sampling, out to the downw:nd edge of cloud, and there were no <br /> <br />changes in reflect~vity which could be attributed to seeding. <br /> <br />A schematic of the cloud and barrier in two dimensions is shown in Fig. <br /> <br />5. The seeding locacior. a~d the X-Z location or the research ai~craft during <br /> <br />- ~ - <br />