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<br />.-t: <br />- -.... '?--.. <br />particle concentrations at the seedline were not clear until background .- ;r ~ -. <br /> <br />concentrations had decreased 1:0 10-20 L-1 on the 2D-G, and 2 L-1 on the 2D- P. \- .~ \ <br />y- ~7 <br />Then increases to 30-40 L-1 on the 2D-G and 6-9 L-1 on the 2D-P were observed ~ ~ <br /> <br />at ::ne seedline from 55 to 92 min after seeding in a cloud with droplet ~ \ ~ <br /> <br />concentrations of < 40 cm-3. If CO, had been used instead of AgI. the effec ts ' ~ '(:.('\-~ '. <br /> <br />of seeding would have been below the altitude of the research aircraft before K~ <br />'c, . <br />. <br />..-('0..., <br /> <br />;;;~~ <br />~~l( <br />< <br />'- <br />< <br />c> <br /> <br />ascent of the seedline rr.atched t~e slope of the barrier. <br /> <br />Increases in <br /> <br />the high natural particle concentrations had decreased to a level where the <br /> <br />effects of seeding could have been obser~ed. <br /> <br />Also CO2 may have been <br /> <br />ineffective on this day consicering the low liquid water content observed at <br /> <br />the seedline. <br /> <br />The final penetration of the seedline 10 km from the do~~wind edge of <br /> <br />cloud, Fig. 4, still showed a high concentration of ice nuclei, suggesting <br /> <br />seeding effects would be limited by ::he dimensions of the cloud and not by the <br /> <br />arr-ount of seeding material released. The unscavenged nuclei at the downwind <br /> <br />edge of cloud will pass over the barrier. If they enter another cloud system <br /> <br />they could be expected to contribute to the ice formation process in that <br /> <br />cloud. Thus, these measurements lend credence to predictions of extra area <br /> <br />effects from seeding with Ag~ (Brown et al.. 1978). <br /> <br />All:hough the goal of documenting ice crystal nucleation at _6oe with AgI <br /> <br />NH41 ~H4Gl04 was not met, this case presents an outstanding example of the <br /> <br />ability to track seeding effects for a long period of ~ime. It also suggests <br /> <br />tha~ AgI ~H~I NH4CI04 is an effec::ive cloud seeding agent with properties in <br /> <br />the field which exceed those measured in <br /> <br />. ,. <br />Cae .laDoratory. <br /> <br />Using the width of <br /> <br />the ice crystal plume on the last penetration, 7 kQ, the 40 km long seedline, <br /> <br />and ass~ming the ice crystal curtain reached ~o the surface, 2.5 k~ belo~, the <br /> <br />1 ' <br />