TM 11-6660-218-12
C2
zones during the spring, the summer, and the fall
ML-367/AM (fig. 126). Connect the
months.
launching reel as follows:
c. Wet and Dry Bulb Reading ,from Psychrometer
(a) Unwind about 5 feet of cord from the
launching reel. Double the unwound
ML-224.
(1) After checking to assure that the wick of
cord and tie the end securely to form
the wet bulb thermometer is wet, whirl the
a loop.
psychrometer; hold it to the front of the
(b) Wind 1 feet of the doubled cord back
body at waist height for 15 seconds and
on the launching reel.
read the thermometers.
(c) Place the unwound cord under the
(2) Repeat the above process until the wet bulb
spacer and securely tie the cord end to
indications change less than 1 between
the top of the radiosonde parachute.
readings.
(d) Tie one end of a doubled short length of
(3) Repeat the process at 5-second intervals
16-ply cord to the eyelet in the opposite
until the minimum wet bulb indication
end of the frame. Use this cord for
is reached.
tying the launching reel to the sounding
(4) Record the lowest wet bulb indication and
balloon after inflation.
the dry bulb indication to the nearest 0.1
l. Inflation of Sounding Balloon with Balloon
Centigrade.
Launcher.
(5) When operating at temperatures below
(1) Assemble the balloon launcher as described
freezing, the wick is wetted 10 to 15 minutes
in TM 116660-23815.
before use so that the heat of fusion of ice is
(2) Place the balloon in the canopy, position
dissipated before the readings are made.
the train line, and insert the inflation nozzle through
(6) Note the readings from the wet and dry
the canopy and on to the neck of the balloon.
bulb thermometers and record the informa-
(3) Connect the gas meter and the gas cylinder
tion on the proper DA forms.
to the balloon nozzle as described in TM 11-6660-
d. Surface Wind Direction and Windspeed.
23815, and prepare the balloon for inflation.
(1) Hold the anemometer in an upright, level
(4) Tie and seal the balloon and launcher as
position. Keep the instrument away from
described in TM 11-6660-238-15.
magnetic material because such material
3-3. Surface, Visual, and Electronic
will cause a false compass indication.
O b s e r v a t i o n Procedures
(2) Turn the anemometer slowly back and
The procedures given below will be used to make
forth until the index mark on the wind
weather observations during normal operating con-
vane is in alignment with the index pin.
ditions. Record all readings in each step. These
(3) Read the compass. The compass card
readings will be used to fill out the appropriate
marking directly in line with the index
DA forms.
line on the compass is the indicated wind
a. Atmospheric Pressure. Read the atmospheric
direction.
pressure from Barometer ML-102(*) (figs. 1-9 and
Note . Wind direction is indicated in relation to
1-10), to the nearest tenth of a millibar, after
magnetic North and must be corrected for Iocal
tapping the barometer slightly to see that the
magnetic declination to obtain wind direction in
pointer is in eqiuilibrium. View the pointer with
relation to true North. The correction in magnetic
degrees for the magnetic declination at a particuIar
the eye directly above the pointer.
station will be supplied by the commanding officer.
b. Surrounding Temperature. To determine the
(4) Record wind direction in tens of degrees
surrounding temperature, read the appropriate
front true North. and convert the compass
thermometer. Use the void weather thermometer in
readings to an azimuth reading in hundreds
arctic regions at all times, and in temperate zones
of rnils (fig. 32). Enter this data on the
during winter months. Use the tropical thermometer
proper DA forms.
in tropical regions at all times, and in temperate
3-8
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