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<br />--....-,--'--:~. <br /> <br />',' <br /> <br />hy <br /> <br />tlu:. "C:"'/.:rlt.IL (\j,u ,:\~~.., H/,-'''' r~-.~t"'.:f (:i.J"..I'...../~t1J...r::. EVlfIIlAf,c.... l("rrOJ,-r" <br />1'\'.Q,~'I;..tr-; R.w. $,1." tI....; A. (.u..'rf ., JJ. HA".. "I.......J - 1~7h <br /> <br />h-c..lIt' <br /> <br />6. SUHHARY DISCUSSION AND RECOHHt:NDAT J(J~~ <br /> <br />The principal conclusions arrrlved 3[ <:-:1 the basia of the overall evaluation <br /> <br />are: <br /> <br />1) There wae no significant d1f(erencp in the net taraet area precipitation <br />on seeded flxperimental daY9 and chat on ll(lr-s'~(:di!d experimental days. '!'his null <br />effeet was apparently due eo the.mlx1nR of positive and negative seedins eftects. <br />Nesativ. effects oceurred vhen seeding was conducted during out-at-bounds condi- <br />tion. and poddvll affaeu occurred ",hen ael!dil1& was c2_nducted du_rInl in-bounds <br />condition.. The flndings discussed in items 2 through 8 below are bssed upon <br />d1agnonlc analyses (Bee Chapter 5) of ,ix-hour hlock predpi.taei.on daea rather <br />than on the 24-hour up.rim.neal day data. Thts rermiteed the aortinl out of <br />the v.rlou. effect. of .eedins. <br />Z) During the 141 expf!.t'hl'le.ntBl days, stable orog;raph1c. clouds pte'lI:t.il.~. <br />about 52% of the time and accounted for about 33% of the experimental day pre- <br />cipitation (at KOJ) covered by the diagnostic snalysis. This stable orosraphlc <br />cloud category includes csses with shallow unstable layers no thicket than 7S mb. <br />ExcludinS the stable ones, case8 Tense mostly from neutrally 8table Btr.~1fora <br />clouds to ones cont.ininS embedded ahallo,", cumuli or atratocumulus. During 37% <br />of the time, or about 10% of the diagnostic an~lysis experimental day precipita- <br />tion, Warm top atable cloud. occurred. lihen these were seeded, aubltantial pre- <br />cipitation increa.es occurred in the tar&et area and art the downwind flank. <br />During 15% of the time, or about 23% of the experimental day precipitation, <br />atable orographic clouds whose tops we(e colder than -29C occurred. When these <br />were eeeded. decte~ses in prccipitntion occurred. The decreases were ~arked <br />when the cloud level t.l1nd component normal to the barrier was strong and the <br />cloud deep. It the t.lind component normnl to the border \.IllN weak and the cloud <br />.hallow, then increases occurred in the cold tnp category. Thls latter effect <br />had nOt been anticipated from earlier cl'oud seeding tests. <br />3) During approximately 48:4 of the time, nnd accounting for about 61% of <br />the experimental day precipitation, the air mass had sufficient thennodynam1c <br />inlltabUity to be considered out8ide of the 8["hie oroguphic category, Le.. <br />deep convection was pre8cnt. Seeding und~r these conditions may have resulted <br />in an increase in precipitation on doYnlolind slopes, particularly when the normal <br />wind component Wtl~ 10101. It l'r"hably resulted in decreases on the upwind slopes. <br /> <br />{l-J <br /> <br />14 <br /> <br />A-ll-S <br />