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7- : . I PI 100s. I P2 180s. I P3 347s. I P4 51Os. , ;:7'. :~~W~:~;*~lli~m~= I . IIrilflltlll!lltll r1l1l1lilLllIllLllI :!:;i~'i~~~~ '~'~ /] :}%illl~:'~1I1 11111 t llllll ~llllllllll t 111111111 \. ~ 11III111I .fj%ilw;~H~i~~lr I GO'! ~ ~l1} 1 ~~1~ (! : r II ~ ~.r ,t}} ~}/ I Ilt,d lU "A II,ftl/11 "'1':"1'1/ :. ~!:*~VNW~~i\~L~~.~fV~1 tlt'Jtrll rnurHI rrl rn~Li~rtl-- :~ i i~R #{~~H ~~;~~~ i~ I \:~ :1 'Pl.1 joflolrlLlrrr~HI ~rlHflll-l Figure 5. 2D-C images of the ice crystals on 2 December 1989 during the testing of the P. syringae nucleant. The multiple vertical lines in each panel are 800 Jim in le~gth and caD be used to size the particles. The elapsed time between the imaging of the particles and the time of their generation appears at the left margin of each panel. 1102(,25 1(1 o~ -, ~I 20h:-, o ~ 103037 250 200 t 150 <- "(i 100 ~ ~ so z o 2:~ 103636 100 50 300 o 100 (bill sile, l..un) Figure 6 The total number of particles in each bin on each pass during the second test of the P. syringae nucleant. The totals are over the 5 secs centered on the time of maximum measured crystal concentrations. The images for passes 3, 4 and 5 suggest a different story. Many small ice crystals are evident during pass 3 and these particles grow larger with time while maintaining their relative uniformity in size. This appears to be a seeding signature. Further quantification of the apparent signature is made in Figures 6 and 7 in which particle totals and mean, median and modal particle sizes are presented, respectively. The plots are for the 5 sees of each pass that is centere~ on the time that maximum 2D-C ice crystal concentratIons were observed. Plots of the total number of particles in each bin over the 5 secs centered on the peak crystal concentration show nothing noteworthy for the first two passes following release of 100 gms of P. syringae. The third pass at 103037 PST shows a dramatic increase in the number of ice crystals, especially in the size range of 75-100 Jim. The fourth and fifth passes show a lesser number of particles but those that remain have grown larger with lime. With the exception of the first two passes in which no signature was noted, the plots resemble a normal distribution. Plots of the mean, median and modal ice crystal sizes in Figure 7 show that these measures are nearly equal within each of the last three monitoring passes. This near uniformity in particle size suggests a common temporal origin for these ice crystals n_ in this case, nucleation by the organic nucleant when it was released from the seeder aircraft. fU!(.!S ~ 1(10 100 1M 2M "'=' o r~ o I""" m 100 200 iQ 100 2M ~~ ~ 100 200 Bin Size (,:tm) J\lc:ln :: Mcdi:lI1""", ~f<j{l;rl // Figure 7 Mean, median and modal particle sizes for each monitoring pass. These statistical measures are for the 5 secs centered on the time of maximum measured crystal concentrations. 131