WMOD00288 ‎(3)‎

• Title: Atmospheric Tests of an Organic Nucleant in a Supercooled Fog
• Date: 12/2/1989
• State: CA
• Country: United States
• Weather Modification - Doc Type: Report

.J1Y -.

seeding track was normally 3 to 4 km and the flight legs of
the cloud physics aircraft within the fog averaged about 1
km either side of the track of the seeder aircraft.

Since the MOLAS effort has demonstrated the
reality of APIPs (reports in preparation), both the seeder
and monitoring aircraft were flown at relatively low power
settings to minimize any possibility that the aircraft
themselves would produce ice crystals that might be
ascribed erroneously to the organic nucleant. This potential
problem is something that must be considered in all future
cloud physics studies that make use of aircraft platforms.

The hydrometer q:mcentrations, sizes and habits
were determined using three probes manufactured by
Particle Measuring Systems, Inc. of Boulder, Colorado, that
are flown routinely aboard the University of Wyoming King
Air 200T aircraft. These include: a Forward Scattering
Spectrometer Probe (FSSP), and OAP-200X (lD-C) and
OAP-2D-C (2D-C) probes. The FSSP detects particles up
to 30 JLm in size in increments of 2 JLm, the ID-C detects
particles up to 187 JLm in diameter in increments of 12.5
JLm, and the 2D-C detects particles up to 500 JLm in
intervals of 25 JLm. Water contents within the fog were
estimated using Johnson-Williams instrumentation. More
informatIOn on the University of Wyoming King Air data
system can be obtained by referring to Endsley ~l .aI.,
(1986).

3. TEST RESULTS

On the day (2 December 1989) of the P. syringae
test flights, supercooled fog covered the lake surface and
the valley to the east and was banked against the Sierra
range to the immediate west (Figure 2). Fog top was 2060
m MSL at a temperature of about -80C. The temperature
rose to over + 80C only 500 m above the fog. A partial plot
of temperature versus height is provided in Figure 3.

I ... ~..... ..-".... - ~~.

J .... ._: . :~~.
r .....
. .. ,..
r_:~t,,-~~- ,.r...I!.......~-.. .I\"~.......
1E:~If......._~~:~~ .. ~ 11.'1:""":

r . . ."!jl.........
:": .."T."i'~"=- .

-.

~- '.-.-....
..... I. -J .

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Figure 2 Photograph above the supercooled fog
over Mono Lake on 1 December 1989.

Temoerature vs Hei?ht over Mono Lake on 2 December 1989

3500 h

.5 3000 n
.i:
eL
~ 2500-.

... c%
~
,,~
J-

2000 n

-9 .8 -7 ~ -5 -4 -3 -2 -1 0 +1 +2 +3 +4 +5 +6 +7 +l! +9

T("C)

Ei~.ure 3 Plot of temperature (OC) vs height (m) over Mono Lake on 2 December 191\9.

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