WMOD00403

• Title: Special Regional Weather Modification Conference Augmentation of Winter Orographic Precipitation in the Western US
• Date: 11/11/1975
• Weather Modification - Doc Type: Report

ground in the
upwind valley.
However, high-
est concentra-
tion of effec-
tive nuclei is
at plume top, or
cloud top, due
to the exponen-
tial increase in
numbers of effec-
tive nuclei per
unit mass of
nucleant as the
temperature de-
creases. The
ground plume
serves as a sort
of reservoir or,
pool which can
either be grad-
ually dispersed
, aloft into the
southwest flow
or can be entrained into a
frontal system and then trans-
ported in the air aloft over
the target area. The preva-
lence of this mode led to the
unintentional westward dis-
placement of the pattern of
seeding effect commented on
above. It also introduced a
condition of self-contamina-
tion in which nuclei that had
drifted far to the west in
the valley eventually became
entrained into a frontal
system moving eastward over
the target area on the day
following the seeded day.
When this following day was
declared experimental but-
not seeded, it became
contaminated.

In the upslope stable
mode all of the nucleant is
immediately driven up the
slope with the plume spread-
ing vertically and entering
the orographic cloud. The
highest mass concentration
is on the ground with the
highest concentration of
effective nuclei at plume

".. - '
I "'-- -
I "

"
'"'
-~

,-
\ \
I \
I'~~- / \
, \
, IAN LUll \
l VALLEY
\

t-}
c(

,
\
1.3 *) . ' . ~ ~;og~~~gu~OO_D ,i

~L.2!.AD.2.. _ _ _ _ _ _ ..._ ...... _ ~ _ - -.... ... - .
NEW /lEXICO , - r .
\ . \ '
\' \... &4t
., a ...
\' ...."'" ....
\

,.
.

ElliUREJ&. FOUR YEAR SEED - NO-&EED DIFFERENCES (l1li/6 HRI)
FOR COLD CLOUQ"T~~ CASEI (T ), -Zl ~) AND STROHG NORMAL
WINDS (VN 1 6/.. IV I).

rtrf' ,/' /
SAIl JlWl \. ,\.
, It;.~,.. II tY,''':Slfi>;,,1 "t~

, ... .::::-.... ~,' mIlE' ·

-~l ..~_.._---' /?
HOP. I zornAL '.... I;;'';:~ - -~-..."
SECTION .....~ AREA somcE~'
'......--
--

POOLING
MODE

r

r - - - ;,-#-'-
~"'l
,.

-.....,.' r-+ t""---
#,' . I
,
.
.

~

UPSLOPE
MODE -
STABLE

-r .......1..lo-
". ,
,.' , c...,
, ' --.. ,., -<

,:;~~:;~-

--

----

UPSLOPE
MODE -
UI~snBLE

'.f:~

~ -{ - -'
-.... ' ,
~", ;'
, ,
.' -,'

;3~: ~
-::- '
~; ,
.".- - - - -----.:;:.

FIGU~ 9, THREE DIFFERENT II0DES - OF T!t~NSPO~T
AriD DISPERSION OF NUCLEI IlI'THE S,'1N JUAN PROJECT.

16

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