Winds Aloft Page: 5 of 20
iii, 16 p. : ill., maps ; 27 cm.View a full description of this pamphlet.
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Wind is air moving essentially parallel to the earth's surface. Winds aloft vary greatly and are
sometimes quite complex. The observed windflow is an important factor in navigation, and this
information is in great demand by the aviator.
Both current and forecast winds aloft information comes into the weather office via teletype
in code form. It also comes over the facsimile machine in chart form. The aviator must be
familiar with both forms of information and must be able to interpret wind direction and speed
at all altitudes.
At altitude wis above mean sea level (MSL), current winds aloft observations are obtained by
visual or electronic means.
VISUAL MEANS
The two visual means of determining winds aloft are pilot balloon (PIBAL) and radiosonde
balloon (RABAL).
PIBA L - A free balloon, filled with helium so that it has a predetermined ascention rate, is
released and observed with a theodolite. The theodolite is similar to a surveyor's transit, and
triangular calculations determine the velocity. The azimuth angle will determine the wind
direction at each level.
RABA L - The winds are obtained in a similar manner as above, but theascension rate is set
by pressure-measuring equipment. In this method, which is more accurate than the PIBAL, the
observer visually follows the radio sounding balloon with the theodolite.
NOTE: These methods are sometimes handicapped by cloud coverage and distances of the
balloon from the point of observation.
EL ECTRONIC MEA NS
Electronic equipment such as radar or radio is used to increase the accuracy of observation.
This also permits winds aloft information to be obtained-through cloud layers and at higher
altitudes. The two most common electronic means of observing the winds are as follows:
RA WIN - Radio or radar is used to obtain the slant range, elevation angle and azimuth angle
to determine winds aloft.
RAWINSONDE - This observation gives a simultaneous measurement of the pressure,
temperature, humidity, winds aloft, and used pressure to calculate the altitude.1
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Snyder, Henry W. Winds Aloft, pamphlet, May 1971; Texas. (https://texashistory.unt.edu/ark:/67531/metapth46574/m1/5/: accessed April 24, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu; crediting Boyce Ditto Public Library.