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<br />The 20 g AgI pyrotechnic flares were expensive and unreliable. In some <br /> <br />batches less than half bur~ed for the 30 s required. Activity tests in a <br /> <br />cloud chaw-ber indicated that the AgI flares produced 100 to 1000 fewer nuclei <br /> <br />per gra~ than AgI burned in acetone (DeMott and Grant, 1986). Also the warm <br /> <br />temperatures, > - lOce, at which seeding was required in the Sierra Nevada <br /> <br />limited the applicability of the flares. Results from seeding with dry ice <br /> <br />were intermittent. Although sometimes the effects were obvious, there were <br /> <br />more times when no effeces could be measured. Yithout an independent <br /> <br />confirmation of seedline interception it was not clear if in these cases there <br /> <br />were no effects, or if the seedlines were missed. Burning an AgI NH41 ~H4CI04 <br /> <br />mixture in acetone presented a good solution to these problems. It is <br /> <br />economical and easier to handle than CO2, The delivery system is simple, and <br /> <br />delivery of see,d,ing mfterial.rcan be ,_d~re.~tbY confirmed by measuring the ~ <br />pvr''''~ ""?t~......4: '('0'-" 1._~J>"cA ~~'"'-<-. <br />temperatureVof the acetone burner. Seeding can be conducted for long periods <br /> <br />of tine with a small amount of material. Activity tests in a cloud charr.ber <br /> <br />indicated that it ~ay produce detectable levels of ice crystals in clouds as <br /> <br />warm as -6~C (De~ott et al., 1983). Finally <br /> <br />since it can be measured with an ice nucleus <br /> <br />the AgI ;oul~ be use,d 8;s '1 F.race~ a. <br />...r 1-.;1. err;,..,.r, ~-.; hl-V",,- .,. ~ N ~"\ tt \._ <br />~ -.I _ "\-'" <br />counter. This paper presents one ~J \-lJ;- <br />" <br /> <br />case study using AgI NH4I 8H4CI04 which demonstrates the activity of this <br /> <br />seeding material and the capability of a research aircraft to find and track a <br /> <br />line source of AgI. <br /> <br />2, Instr~~entation <br /> <br />The researc~ aircraft, a Beechcyaft Super King Air 20GT operated by the <br /> <br />University of ~yomi~g, carried a full complement of s~ate-of-the-art <br /> <br />instrumentation for cloud physics research (Cooper et al., 1984). <br /> <br />Instrwaents <br /> <br />, <br />- 4 - <br /> <br />'it ltw'- <br />J.~ ~ <br />43 <br />r:o~:d ' <br /> <br />. ....~ <br />--..1 ~' <br />'" ".~ <br />, ,,", <br />f~' <br />v-.... r ~ <br />t' ,. <br />, J:'W-- b <br />\1: _, <br /> <br />~~.-): <br />-' i..j\~ <br />(p. <br />