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<br />However. these resolts do not stand Out clearly above the background variability
<br />in precipitation.
<br />4) During some hours on experimental days. blocking type flow prevented
<br />the nucleant from the ground generator network from ascending o~er the target
<br />area (5.3% of the six-hour blocks). there.was total or partial blocking of
<br />e~fective ~ntrainment of nuclei 1n 12.6% of the six-hour blocks, Under these
<br />conditions the nucleant was carried well to the west or northwect of the ta~~et
<br />area. When the following day waa,a not-seeded experimental day, it was often
<br />contaminated by nuclei returning from the west following the br~akup of the
<br />.blocking flow regime <7.6% of the three-hour blocks).
<br />S) Extra-area effects of seeding appear to have occurred Qver a broad area
<br />lying up to 160 km (rom the generator sites.' Much of this effect occurred as
<br />expected. downwind of the target area. during within-bounds wind conditions.
<br />Some of the effect occurred. not 8S expected. well to the vest of the tartet ares
<br />.8 .,result Qf tbe seeding under blocking flow condition.. Over the dovowind
<br />,rea (e.g. "Saa Lu~s Valley) apparent net increasea 1n precipitation are small
<br />!n'absolute'value. No net ,effect appeared at the .buRdaDt atattona in the a~ea
<br />to the west of the target instrumented as part of the original target area.
<br />~:6) Ipsufficient data'were available 1n the stable cloud category to
<br />,~Bta~l~~h emPir1cally,.~~re, the,~.~..1de limit (clo~ top temperature) of the
<br />positive ,effect eeed1n&.V1ndoV;-lay.\"lll the unstable category the 'sound ins
<br />'.' . ,. ,._', . '-. '....r... -.
<br />.\';1der'1~ed cloucl toP'::'U4.~'ADt:;iepreHnt; the 'U\le 'top'. ,::Tt!e_,t'Nt top.. developed'
<br />.' . "', ; .,,-"';, .:-...,~'..._;~,_:",>""~,~-,,,",'.~J::\f;;..: I,'.' ','" .\,-~',,', ':. ..
<br />'. fo~1~1ng the' ,;el~ '.of '1a..~t.&&.~ity 'ov:er' tha"upwind' slopes 'of 'the baTrier;.
<br />., . '. ~ .' < . -, - .
<br />-bence. no uae...nt_.of ~.wa", aide l~lDlt could be 'investigated for this category.
<br />':~:',:a"?,{;~;). se~~~,~,:~~.r~~~:',._'.~Fo~,ta.~ .p~..&e ~d .D~_ eUect ~th.r than chat acco...n~ed
<br />'.Jor.:-by" the, ft.o~t.lllY< associated 'distr1bution of stabillty and \.Iind.
<br />.-....,',.. .... ' . . .' .
<br />,~.~;.,2:'t}8) : .. The' overall paUnchl for precipitation 'enhaneea.ent "as 8sseSged.in this
<br />e~~l~tlon study at aroundllO%. taking into account randomization bias. this
<br />.traaslates into an overall streamflow enhancement potential of around 19%. this
<br />potencial W8S ~ot realized in the seeded 24-hour experiment. I days for several'
<br />. reasons: a) the opportunities lost with late starts in the fall season; b) sus-
<br />pensions. c) missed forecnsts of suitable days. d) losses in the accounting for
<br />experimental day precicatton when strong blocking flow existed and seeding was
<br />ineffective in the t~rget ~ren. e) excess accounting 1n not-seeded days when
<br />contamination -o'ecu-rrcd"o:l ,i 110t-se(:d~d exp~riment.11 day followi~g a seeded block-
<br />ing flo".. day. f) losses when cold top stable orog1."3phic clouds Were seed~d under
<br />strong uind - deep cloud conditions. and s) possible moderate seeding-produced
<br />losses on the upwind slopes I.'hen strong convection was seeded.
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