WMOD00300 ‎(2)‎

• Contract/Permit #: 2-07-81-V0256
• Title: Cloud Physics Studies in SCPP From 1977-87
• Date: 10/1/1987
• Weather Modification - Doc Type: Report

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~__. Seedability

T~e ~05t d~sti"'~tive characteristic ot the deep, stable orographic

C~J~~S over the Sierra bcrrie~ is the

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that

the cloud droplet

concentrations above the aoc level are typically maritime.

wben the

{ 1.=
cc~ce~:ra~ioc ~s cclv

~o ro 30 c~-3 a small vertical displacement of an air

~crce: will result in mean droplet diameters of 20, to 30

Urn.

These

dro~let ~izes are efficiently accreted by ice crystals.

The accretion

process not onlL' depletes the condensate, but also results in ice

~~l~iplication when it occurs near the -SaC level. The net effect in these

stor~s is to produce a~ extremely effective glaciation process in which

very little s~percoolec water passes over the crest line.

With the

cc~)i~atio~ of SICP and riffiing, ~t appears unlikely for these cases that

any seecin~ strategy could be devised which would result in a measurable

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i~crease in precipitation.

~ "' -- ~ ~ ,+ - ,"'- ~~
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'"" . _ ~ ~ ~ ~ -=- 7 __ _~ - ~ ~. -'- ~dt..

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n

'1Q~3' ~ ~ sturl- o~ a GeeD unsta~le orographic
~1c:-...itz \. J'e j presem..e': a case "''1'" :. , -- --

stc:-= wh~ch occurred on 18 Feb 1980.

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3a. Dynamic processes

On rhis ~ay a convectively unstable air rr;ass was present

over the

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~:.e!"rc

berrier. T:le

forced ascent by the barrier res~lted in a number of

se;,~e::-e

t~u~ders':Qrll.s.

The Wyoming King Air was struck by ligh:ning at 1149

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lar_ge as 2 em.. u~l'~,m.eter fel.!.' at the ~adar ~1200
3EC hailstcr:es as ~--

LST.

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:580 ~ST She:-ida~ so~ndi~g is presented in Figure 8.

The cloud

base

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oc a-i ~.e~~rrel -Lhpnry
te!:ipera!:u:-e was 7 '"... _- - -- .:

indicated a -30C lifted index at

500

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