WMOD00413

• Title: Validation of Precipitation Management by Seeding Winter Orographic Clouds in the Colorado River Basin
• Date: 9/1/1993
• Weather Modification - Doc Type: Report

Distance (km)'

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As shown by Rauber and Grant (1986), the "best" ice particle concentration for conversion of
SLW to ice is a complex function of several variables. For practical purposes, the desired
concentration in the crystal growth zone should be at least 10 ice crystals L-I and may be over
100 VI in some situations (this point will be further investigated during the direct detection
experiments). Attaining such concentrations requires that at least part of the SLW zone
through which the ground-released AgI is mixed by mechanical turbulence (and sometimes
weak convection) be colder than about -8 oe. This temperature might be increased by about
2 to 3 oe with newer, more effective AgI, solutions and high output generators. For
ground-based propane seeding, significant ice particle concentrations may be formed in
supercooled cloud at

/""'. 1 5000
+-
Q)
Q)
~
'--"

c
o

+-
o
~ 10000
I.J.J

5000
-20

-24

-8

8

32
6.0

o

16

-16

24

WIND .

-5.5

5.0

4.5

/""'.

E
~
"-""

-- 4.0

-3.5

c
o

3.0

+-
o
>
Q)
W

2.5

2.0

-15

-5
Distance

o 5
(miles)

10

1.5
20

15

-10

Figure 1. - Conceptual model of orographic cloud with SLW zone and AgI seeding plume.

temperatures slightly colder than 0 oe. Previous measurements suggest the crosswind spacing
between AgI generators or propane dispensers should be no more than 2 to 3 km to affect most
of the crosswind extent of the SLW zone.

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