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<br />'"
<br />
<br />3.
<br />
<br />DATA ANALYSIS
<br />
<br />~
<br />
<br />In addition to the Measurements of the
<br />",.ass of AgI used (known from th... number of flares
<br />cropped or. the durution of tJa~t! ~c~dlng)t the
<br />g":aclated cloud volume aou typlcill crY.::Jtnl con-
<br />centration need'to be men~urt!d or estimated to
<br />c.!.~tcrn\lue th~ effect:tvcnc~::li of AgI .1.n creating
<br />!.cc crysta.t::J. Moreover,.lt!t:I lto..!ceM::liSry to dcter-
<br />!!!ine thnt natural ice concentrations arc small
<br />compared to that calltH~d {)y th~ seeding.
<br />
<br />The cloud volume was usually considered
<br />:0 '>e a rectilinear solid with length and width
<br />determined by track lengths and '>y photosol an..!
<br />t~ickness estimated by h...ight a'>ove the 0 C level
<br />an..! by photos. In th" flare cas...s where only
<br />downdrafts or stationary air w"re encountered by
<br />the upper aircraft. the top of the volume was
<br />considered to b~ the ::seeding-level. In two base
<br />seeding cases where a seedIng pul::se rose through
<br />the sampling level. the aVerage pulse rate of rise
<br />.>..enrl..tht:'.pul~e duration were u::ied to determine th~
<br />thickn~s~ of the affected volu!r.C:. .Si.ich'''tci'rinf:mfttl1:s'
<br />result in smaller calculated values of effectl"'"
<br />
<br />iveness.
<br />
<br />The crystal concentrations were: deter-
<br />mined by the IPC inst!'l1Ulent~ us.tng a linear aVer-
<br />age act'uS:3 the entlre clouJ fur each pa::;::i. When
<br />many ?a~ses were mad~l those ::ie.!.ected a~ t'epre-
<br />sencat.lve were at t:lmes lnt~ c:nough to ullow the
<br />crysta~.::; to spr~ad i.lpprt:ci.:lb~y throughout the vol-
<br />UII1t::, yet early enough :iO th~lt the m.."iJority of cry-
<br />stals had not fallen to lev~ls bel.ow the sampling
<br />level. It was aSMltnlcd that the cry:ital::i fil.!.cd
<br />the vertical cloud d.lmension cescribed anJ. that
<br />the natural background of lee crystals did not
<br />increase during tlie exper!.~nts; the::ie owy not
<br />always be good a::i9Umpt..lons. !Iowever, in the cases
<br />t!~scribed in detilil b~low it was v~rifted that the
<br />crystaL'i did distrit>ute th~~~se.tv~s horizontally
<br />and vert:!.cally throughout :hc descrl!.led volume.
<br />Furthermore, ~tcPLlrtLmd et a~q (1977) have shown
<br />that natur.al ice cry~tHl c'-"'l"!~entratl()ns rare.ly
<br />inCreLl::i~ with tlme to vlllu~::i CllClllUlCere=d ilttlo!r
<br />::iccI.U.ng in t.he types of clu~cs c.hosen for seeding.
<br />
<br />The 1n!.t:~al effectiven~ss c<J..lculatlon::;
<br />",ere adjusted for t.he cry::i:.al counter llLlrr.l.u.lization
<br />values t as given in Tabl~s : and 2. Corrections for
<br />the ab:Jolute Coufit:tng efficiency were not known for
<br />any of the instruments.
<br />
<br />4.
<br />
<br />DISCUSSION OF, T!!E ?Y!l.OTECnnC CASES
<br />
<br />Data on'the NEI and Navy flare s...eding
<br />cases are presented in 'iab:e 1. Omitted Er-om the
<br />table is an NEI case on ,t!l July for which the
<br />filters detected AgI only on tIle 'pass immediately
<br />after seeding. Strong uovncraEts were measured on
<br />all passes, which apparently transported any
<br />resultIng ~.fYstal~ below thu ~ampling level so that
<br />only 0.1. R. ,prt!:~umably nu~ur3.1J were ob~erved.
<br />The crystal concentration in cloud 3 of 2/. June was
<br />measured on only ont!: pas::! after seeding; the hIgh
<br />crystal concjntration encountered on th~ pre-se~ding
<br />pass (1,3 ,~-l was subtracted to yield the quot"d
<br />vu.lue of 4/. 1-1, which may sttll conta.ln t!ome
<br />natural crystal::;. Resu.!..t.::i from thi~ c~st: tihould
<br />obviously be u~ed with caution.
<br />
<br />......, ~ ~ ......._. _..1.11....__ a........
<br />_ .., _I. U,_,- ......110
<br />~~~,. :::. ~~~ ~::\ -;;: ::::~;'" 10:::::;:'&1 ~:~'c '~~~t~'
<br />
<br />...
<br />
<br />(1_.... _I.' ._<1_. .'U ..'.1,
<br />
<br />-1...1...
<br />. .' ~ 1.1 ...
<br />
<br />,.,,1.11
<br />
<br />.J. ~.:.~' \ :
<br />
<br />Jill 1M' J
<br />
<br />J"."II
<br />
<br />.... ':
<br />I
<br />
<br />..,.. ",\'1.'.
<br />-=- .
<br />
<br />l,t...'1
<br />
<br />.....J ...t.t.l.
<br />-=.. .
<br />
<br />-.
<br />~"',
<br />
<br />(1_...._..........-..1.......11....
<br />
<br />,
<br />- III I.
<br />
<br />1,'.1.1(
<br />
<br />..'tl.I....
<br />
<br />',....1)
<br />
<br />..,.,.,.
<br />".I~'.'." _..
<br />
<br />JI 1M, ,
<br />
<br />1....,,"
<br />
<br />_~~ _.... I.'.
<br />.:- "
<br />
<br />:::':
<br />
<br />I" "., ..,1_ _, _1__. .....1.. _. ._, I_II
<br />
<br />I
<br />
<br />The effectiveness values for the two flax'e
<br />types are plotted in Figur" 1 and are there compared
<br />with the laboratory curve:J t \Jlt!l \J~!ch th~y are in
<br />r~asonable ugreE:ment. ThE: points .<ire plotted at the
<br />sampling temperatur~s. an,! tbe cold extremity repres-
<br />ents cloud Jor. ~he warm ex~r~mi~ies are arbitrarily
<br />. 'druvm: ,'Bt,---5 C..- ..'!'Jte "effec.t.ivcncss error bars reflec.c
<br />the maximum oh9~rv,ut.ional e=rror t:aclmat.es. Rowevet.,
<br />actual errors may be great.er cut: to some of the
<br />a~sumptlons invo:vec in the culcu~ation~. Effective-.
<br />ne::ss values determined for the. drj ice seeding cases
<br />(Super ~'. 1977) are plotted for comparison.
<br />
<br />...1
<br />
<br />.'oT
<br />
<br />10"
<br />
<br />D
<br />..
<br />%1014
<br />
<br />'n
<br />, 1;
<br />I to
<br />~ lO'l
<br />on
<br />.,
<br />~
<br />
<br />~ '01~1
<br />
<br />~ CO~
<br />lOll p-
<br />I
<br />
<br />T
<br />
<br />---l
<br />
<br />I
<br />r;b~
<br />/:~FF~ ,
<br />~J----
<br />-:7!.J. ;:'1
<br />~O! }
<br />
<br />- I 1 I I , , I , , , I I
<br />-0 -10 .r~ -20
<br />TEUPERATURf .C
<br />
<br />
<br />,.
<br />'.
<br />
<br />Figure I The effectiveness of two types of Ag!
<br />flares. The curves arE: for the la~oratory
<br />values of Ca~Jey et a1., 1976. !he thin data points
<br />are for NEl f~ares l the chic:, for ~avy flares.
<br />
<br />Filters exposed for ice nuclei in the
<br />upper portions of the 20 July seeeec! cloue sllowed
<br />higher than nor~al concentrations (presuma'>ly AgI)
<br />in the presence of ice crystals. A sample of an
<br />adjacE:ot natural turret of similar character
<br />showed only bac~<groulld nuclt:l and no ice' crystals.
<br />
<br />The 21 July cloucs 1 and 2 were a part of
<br />the same complex; cloud 2 was a later turret. There
<br />is a possibility that the first 9ceding with Navy
<br />fIaree contmn:~n.:tted the clout! portt,;n u~ec! for the
<br />NEI flares as the entire ca~c lacks photographic
<br />
<br />,J
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