TM 11-6660-218-12
h. Upper Air Pressure, Temperature, and Rela-
evaluates the data received by the radiosonde
tive Humidity (Electronic Observation). The ob-
recorder for pressure, temperature, and relative
server on Radiosonde Recorder AN/TMQ-5(*)
humidity and records the data on DA Form 4197.
Section Il. METEOROLOGICAL DATA TECHNIQUES
elevation angles from each zone. When
3-4. Use of Visual Observation Data
the pilot balloon is released from an offset
a. Ballistic air densities and temperature can
point, more than 50 meters from the ob-
be determined from surface observations of pres-
serving station, enter the data on the
sure, temperature, and wet bulb depression when
zone wind plotting board (fig. 33 ).
the station height is above sea level and the time
Enter the horizontal distance readings in
(2)
of sunrise and sunset are known.
column 4 of DA Form 4469.
(1) The surface data initially recorded on
Plotting Board ML-122 is oriented by
(3)
DA Form 4524 are used to determine
placing NORTH directly away from the
ballistic density for each line of the
plotter. Rule ML-126-A is then placed so
message.
that the edge which is in line with the
(2) The station pressure is recorded to the
pivot hole passes over the appropriate
nearest millibar.
azimuth on the plotting board (fig. 3-4)
(3) The temperatures from both the wet bulb
for the zone indicated.
and the dry bulb are measured to the
(4)
Mark the pilot balloon position on the
nearest 0.1 Celsius with Psychrometer
plotting board with a small capital T op-
ML-224.
posite the horizontal distance. The top of
(4) The altitude of the station is determined
the T is placed along the edge of the rule,
to the nearest 10 meters above sea level.
and the stem of the T is placed at the de-
b. Ballistic temperature is determined by the
sired horizontal distance. Each point
surface observation and entered on each line of
plotted is identified by the zone number
the message. Express this value to the nearest 0.1
at which the angular data was read. If
percent of International Civil Aviation Organiza-
the plot is made at other than the normal
tion (ICAO) standard. The temperature change
scale, the factor by which the distance is
with height will be made in accordance with the
expanded or reduced is shown after the
ICAO atmosphere lapse rate. The virtual tem-
zone number by writing a multiplication
perature is determined in percent of ICAO stan-
or division sign and the factor used.
dard and recorded on DA Form 4524 in degrees
The direction and windspeed at the sur-
(5)
Celcius.
face level is determined with the hand
c. Ballistic density is determined by the use of
anemometer. Convert the azimuth read-
departure tables and entries made in blocks (8),
ing of the compass reading to the nearest
(9) and (10) of DA Form 4524.
100 roils, as described in paragraph 3-3d.
Read the windspeed directly from the
d. Departure from mean surface density is
anemometer to the nearest whole knot
evaluated from artillery tables and blocks (11)
and enter this data in columns 7 and 8 of
and (12) of DA Form 4524.
DA Form 4469.
e. Departure from mean ballistic density is de-
termined to the nearest 0.1 percent for each line
(6) The zone wind directions for zone No. 1
number required and entered in block (14) of DA
and higher are read directly from the
Form 4524.
plots; use Scale ML-557/UM. A line is
drawn from the zone entered over and
f. Percentage of standard ballistic density is
beyond the next point; then, the direction
entered to the nearest 0.1 percent for each line in
is read on Scale ML-577/UM. The center
block (15) of DA Form 4524.
of the pilot balloon scale is placed over
g. Determine the zone wind direction and speed
the point of origin, or the plotted point
by using the information given in columns 1, 2,
where the pilot balloon entered the zone
and 3 of DA Form 4469. The zone windspeeds and
being considered.
directions are plotted as follows:
(1) Compute the horizontal distance in
(7) Scale ML577/UM is oriented with
meters; use the artillery tables and the
NORTH on the plotting board by align-
Change 8
3-11
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