WMOD00176

• Project Name: Annual Report
• Title: Seeding Operations & Atmospheric Research, 2005 Annual Report
• Prepared By: Duncan Axisia
• Date: 12/31/2005
• Weather Modification - Doc Type: Report

.
.
.
.
I
I
I
I
I
I
I
I
I
t
t
t
t
t
t
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
~
.
~
~
I
I

''''f", 0...,

.-.-..
>IOOcoum...cc

'-,

.-.

~
.
.
l
<
.-.
~..

.-

-

-_.

--

-_.-
..... -:

,-'--
. .

'"

"

.

COPE~'MOo_"'"'(""'1

.,,' ;~~.l~: ..h.... I .-.-..
. elF' E", "~[,,.~,...
>l00couma:cc
,- "~
.- . .
"
.-
-- .. -- 1
._.
.
I . . . '" -.
<
.-. - .- . . . .. "
.- . -
,_. . .. . j
-
"''':
,-
" ,~ ,-

U~'_O"om~(""')

Figure 17; (d) Cloud droplet effectrve diameter IS plotted as
a func:tial ofalbtude 10 illustrale how" the dropieldJametefs
vary 1Mlh dOJd depth: (e) CXJl1llQSite of droplet effecbve
diameter and precipitation hydrornelOO' diameter plotted
WIth altitude to demoostrale precipitation fcrmaboo.
Hygroscopic Seeding Tests

Not all clouds are responsive 10 the same
seeding technique and the same seeding
agent. On-top seeding with silver iodide flares
is thought to work best on vigorous convective
clouds having some coalescence (Rosenfeld
and Woodley. 1993). It apparently is not as
effective on highly continental clouds
containing high concentrations of very small

supercooled cloud drops (Rosenfeld and
Woodley. 1997). A different seeding technique
and seeding agent is needed for these clouds.
Recent developments suggest that this likely
will involve hygroscopic seeding of individual
convective clouds, aimed at improving their
precipitation efficiency by enhancing the
coalescence process,

"

During May and ear1y June of 2005 Drs, Woodley
and Rosenfeld together with the SOAR crew
conducted several hygroscopic seeding
experiments using milled salt released from an
agricultural aircraft. SF6 gas was released in
updraft from the cloud-base seeder simultaneous
with the release of the hygroscopic salt powder.
The gas was detected on subsequent passes.
indicating that the aircraft had penetrated the
seeded plume. The detection of the gas was
successful in part due to a software program that
ingests the seeder coordinates and the research
aircraft coordinates and directing the research
aircraft towards the location of the seeder aircraft.
Although the data is still being analyzed, it is
evident that an alteration of the cloud droplet
spectra near and above cloud base, as required
by the conceptual model, was found within the
seeded plume. During the Texas experiments,
such a seeding signature was observed as a
broadening of the precipitation particle spectrum
as measured in the Cloud Imaging Probe (CIP).
This is shown in figure 18. More cases are
needed in order to draw any firm conclusions.

z0050531

,~ !

-".,~".,:,
.

2!.l~' "21

-.,.;.'.",'

g to!
'! 'r
" I
. "'
~ r
e '
. COI,
" ,
~ COOl r
Il:; ~
COOO'r
,

-......,..
-:'.'~~..

.. ,

1

'D"
,

'D '00 lllOO
Dmlcron

Figure 18: Droplet and precipitation spectra 3000 feet
above doud base at a location ....mere SF6 was
sensed by the researd1 aircraft A ~ible seeding
signature is noted by the observation of a few drizzle
drops at the trailing edge of the spectra aI21:43:532,

32