WMOD00490

• Title: The Effects of Mountain Lee Waves on the Transport of Liquid Propane-Generated Ice Crystals
• Date: 9/9/1996
• Weather Modification - Doc Type: Report

1453

108

120

REYNOLDS

5000

SEPTEMBER 1996

112

116

115

111

107

103

FIG. 23. GUIDE-predicted plume from site 7 overlaid onto terrain
contours for 9 February 1993. Aircraft-observed SF6 concentrations
above 10 ppt noted by symbols. Seeding plume noted in Fig. 22 is
annotated with the time of 1853 along the ridge pass. Boxes well
outside the seeding plume are noise associated with aircraft begining
or ending a turn (box, 10-15 ppt; plus sign, 15-50 ppt; cross, 50-
100 ppt). Scale along outer boundary is in nautical miles.

The model has 5-km horizontal resolution and 100-m
vertical resolution. In contrast to the method used by
Rauber et aI., the horizontal winds are derived by sim-
ply extrapolating the winds measured from the Johns-
ville rawinsonde across the model domain. Flow chan-
nels are not used. Cloud liquid water is a user input and
is held constant over the model domain. Crystal growth
rates and fall speed calculations are identical to those
described in Rauber et aI. Vertical motions are crudely
modeled by multiplying the component of the wind
normal to the model terrain by the slope of the terrain
between model grid points. This method of calculating
vertical velocities may only be valid within a few hun-
dred meters of the terrain. Based on the results pre-
sented in section 2, it may be possible to better simulate
vertical motions at elevations above a few hundred me-
ters from the terrain, as will be described below.
GUIDE model-predicted crystal trajectories for ice
initiated from sites 7 and 9 using the 1800 UTC sound-
ing and for site 7 only using the 2100 UTC rawinsonde
data for 17 February 1993 are shown in Figs. 24a and
24b, respectively. To account for the effects of the lee
wave, the vertical velocities as shown by the up or
down arrows in Fig. 24a were input to the GUIDE, as

4000

T"
..
:t'
t1
Tt
/
t
t'
,1 .ACFT

.. .ACFT
- <.. ~/~"~ .-. :-.-: .-. :-.-:.-, --
- \
,
.

.3,3'C

EXPLANATION
t1 m/s

:[
10 3000
'"
...
:I:

20"

-8,5'C

.6,1'C

2000

15000

O,5'C

1000
-10000 -5000 0 5000 10000
5000
. .
.
.
4000 EXPLANATION . .
t1 m/s ~
.
:[
10 3000
'"
...
:I:
2000
1000
-10000 -5000 0 5000 10000
Distance from JVL (m)

-5,9'C

-3,5'C

-1.6'C

O'C

15000

FIG. 24. (a) GUIDE model-predicted particle trajectories from
sites 7 and 9 using the rawinsonde horizontal wind field and the
vertical velocities from Fig. 25 for 1800 UTC 17 February 1993. The
2iT line for site 7 denotes the model predicted top of the expected
SF6 plume. A temperature profile up to 3000 m is shown on the right
of the figure. (b) Same as (a) but for 2100 UTC for site 7 only.

shown in Fig. 25 for 1800 UTe. The balloon-observed
ascent rates are held constant in the vertical over the
grid box observed under the assumption that the waves
are vertically in phase. Vertical motion values upwind

2700
E
-:: 2400
.r;
'"
';;;
:I:

10 15 20 25 30 35 40 45 50 60
Distance (km)

FIG. 25. GUIDE model contoured vertical velocities (m S-1) across
the project area for 1800 UTC 17 February 1993. Horizontal grid
spacing is every 5 Ian. Rawinsonde-derived vertical velocities are
substituted from 20 to 40 Ian downwind except in the lowest 300 m.