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<br />302 <br /> <br />JOURNAL OF APPLIED METEOROLOGY <br /> <br />VOLUME 29 <br /> <br />surements of IN and ICe. Because the IN measure- <br />ments are blurred by the slow decay time the ICC mea- <br />surements were used to pinpoint the penetrations of <br />SI and S2 and thus calculate advection speeds of 17.3 <br />and 15.5 m S-I respectively. On the second panel of <br />Fig. 7 the seedline age is indicated for each penetration <br />of S I-S3, with the times of penetration and seedline <br />age found using the aforementioned advection. Even <br />though the IN measurements are blurred note that each <br />line penetrated showed definite increases in IN 25-40 <br />s after interception; except for the final penetrations of <br />S I-S3 when the aircraft had descended 300 m below <br />the seedlines where few IN would be expected. The <br />different advection speeds found for S 1, 17.3 m s -I, <br />and S2, S3, 15.5 m S-I, indicate that the wind was <br />slowing with time. Note that the advection speed ofSl <br />matches that found for P3. <br />Measurements by the research aircraft from 1855- <br />1935 are shown in Fig. 8. Table 2 summarizes the pen- <br />etrations of SI-S3. For brevity, only penetrations of <br />S2 will be discussed since they provide the clearest in- <br />dication of seeding effects. The first penetration oc- <br />curred 10 min after treatment and a distinct increase <br />in ICC was observed along with a decrease in droplet <br /> <br />concentration. The penetration at 9 min occurs after <br />the 10-min penetration because the aircraft made a <br />quick turn and penetrated S2 at a point where seeding <br />material had been released 1.5 min after the point of <br />the first interception. This offers a unique opportunity <br />to see the nonhomogeneous nature of a single seedline. <br />The ICC and droplet concentrations are higher at the <br />first point, while on the edge of the seedline at the sec- <br />ondpoint droplet concentrations decrease to O. Sub- <br />sequent penetrations ofS2 were at 19,22,30, and 39 <br />min after seeding. Images corresponding to these pen- <br />etrations (Fig. 9) show the uniform nature of the ice <br />crystals created by seeding and that at 10 min the in- <br />crease in ICC was caused by 50-100 J.Lm particles, sug- <br />gesting recent nucleation. Although the 2D-C images <br />shown at S2 + 10 in Fig. 9 are similar to those in Fig. <br />6, evidence from the liquid water instruments indicate <br />that no large drops were present and hence that the <br />images are likely small ice crystals (Rauber and Heggli <br />1988). Liquid water contents measured at 1900 are <br /><0.1 g m -3. Although the FSSP drop concentrations <br />are similar to the earlier case, nearly all drops are < 13 <br />J.Lm. In the earlier case over half the FSSP drop con- <br />centration was composed of drops > 13 J.Lm. In addi- <br /> <br />52 + 10 2D-C <br /> <br />l .1 ~ ! J ~ j f .l !. ! !. ! ! ! J) U j j J .l !' i ! J ! J .1 .I ! ! !.Li1t.. j I j j J ,I ) ~ ! -J J J ! j ! ! .~ j J ) J ,I f j' ) j. ! ! ! J <br />2D-C <br /> <br />! ,. ! j-t ! II t J ! I f j J 1 .1 ! .1 J.! .1 J !. ! ~ ) J ~ ,l ,~ j ) !' f ! ! ! ,[ ! j .l.t ! ,L ! .l ) J ,l ! ~ J J ! .1.1 J j J ) j. ~ J J ) ! ! ! ! <br /> <br />52 + 19 2D.C I---l 0.8 mm <br /> <br />. ~ r .l ~ f ! J ,l r !. j !. r !. :~ r .~ )' ~ j .~ !, .l i. ]a r f .L !. t !, r .L .l .l ~ t j r .l ! !- f r !. Jar. ) ~ r r !' r j' <br />JIIJJJJjJJJIJJJIJJJIJJJJJIJJJJJJJJJJJIJJJJJmJjIJI)JJJJ)JJJJJJjJJJJJjlIIJJjjjJJJJJJJJJJJJ)JJJJJJJJJJJJJJJJJjjJJJjjJJJJJJJJmJJJJJJJjJJJJJJJJJJJjJJJJJJJjJJJJjJjJlljJjIJJIJjjlilJJlllJIJlllllJJ'lIJllllllllllllJJllJJljJllllll1JJJJJIIJJIJIJJJIIJJliWJHjjllJIJiJJI <br /> <br />2D-P 1--1 6.4 11111 <br /> <br />52 + 22 2D-C <br /> <br />r 1- .l r !. j L r r ! ~ J .l ! r ,l r ,I. ~ r r j' ~ !~ r .~ !. r .r r !. L .L ,~ r r 1 !. r ~ !,. ) ~ !- r ~ ! ~ r ~ <br /> <br />2D-P <br />illlliJ)lllli)JllllJ)))J)IJJJ))IIJII)IJJI))I))IIJ))JJ)JJIII)JI)JIIIWJJJJJIIII/)IIJ)JJJIJI)JJJIIJJJjjjJJI)JJJI)J)J)IJJIJIJllJI)JJIJJIJ!)IIIIIIIIJ)JIIJIIIJIJJJJillliji!11IJJJIIJjjJJJi!)I)/JlJJIIJJjjJJIIIJJJJIJIJJJIIJjJJII)liJI1/IIIII)llIllllllllllIIlllllllllllll)11 <br /> <br />52 + 30 2D-C <br /> <br />! ,~ ~ ~ ~t r f! !- r j ~ ~r L r r r j' i !..l !" ) f'I ), t r ~ j. ~ f r .r t ~ ~ ~ j. ~ r !. ~ t ~ )' <br /> <br />2D-P <br />'jjj il'jlm JJjJJJJJ)J}JJJjjljjjJJt jr)JjjIJ)JJrJ)jlj)IIJI~jjJIHlJJljjjJ}rjj) jjJJtlJIJJJ JIIWlJJJJltlj)rJnJIJJJjjJIJjJ)}JjJJi JJjjJ~ JjjJJIJlf IJJjJJJjjJfflJfjJjjjJfJmIIJjJJjj~mjJI)JjjJJJJJJ} IIIIWI J)~ IllJJiJIJi <br /> <br />52 + 39 2D-C <br /> <br />! r ,I~ j. r rr ;.. t r r .r' ~ ~ r ~ ~ ~ r ~ .r" .i~~ ~ j- .L .l ~ r.w r .rJft j' !. ~ r !- } ! r ) r <br /> <br />. 2D-P <br /> <br />iJJlm.LJmjJlljJtjjl}f!~tljfIJlf)))r JjnHJjjjHJJJrt~IJnHJJ. J~rJI11JJrHI)rIJIJlj)nJ)lliJ)J ill))!IJll] Ilf))ll fJ~lm~JJjJI~nJJjr)II}JJ)jfJfjJI- 1111~IJIJ~lJJILrJJtl.jiljlljjJj' rllj <br /> <br />FIG, 9. Images from the 2D.C and 2D-P on the research aircraft during penetrations ofS2. <br />Only 2D-C images are shown at S2 + 10. <br />