History of the QBO
The Quasi-Biennial Oscillation (QBO) is a
change in direction of mean wind speed in the
stratosphere. The first observations related to the QBO was a result of the eruption of Krakatau in
1883. People noticed that ejecta that made it into the stratosphere seemed to move in an easterly
direction so these winds were deemed the “Krakatau easterlies”.
In 1908, A. Berson launched balloons from tropical regions in Africa and saw a westerly tendency of the winds in the stratosphere, which
become known as “Berson Westerlies”. It was believed that the Krakatau easterlies layover the Berson
westerlies until 1954 when the transition was shown to vary year to year. In 1960 two scientist
independently discovered the QBO, R.J. Reed and R.A. Ebdon.
Reed used rawinsonde data from Canton Island (2.8°S) and observed “alternate bands of
easterly and westerly winds which originate above 30 km and move downward through the stratosphere
at a speed of 1 km per month.” He also noted that the bands appeared about every 13 months which
gave a total cycle time of 26 months. Ebdon used data from Canton Island as well to eventually show
that the period was between 25-27 months as well as using other site around the equator to show that
the changes happen simultaneously around the equatorial belt. Later it was determined that westerly
shear descend quicker and more frequently than easterly shears.
In 1986, Wallace and Holton figured out a way to get a QBO using upward propagating gravity
and other atmospheric waves, this model was later improved by Plumb in 1977.
(Baldwin et al, 2001)
Main Page Basic Model
stratosphere. The first observations related to the QBO was a result of the eruption of Krakatau in
1883. People noticed that ejecta that made it into the stratosphere seemed to move in an easterly
direction so these winds were deemed the “Krakatau easterlies”.
In 1908, A. Berson launched balloons from tropical regions in Africa and saw a westerly tendency of the winds in the stratosphere, which
become known as “Berson Westerlies”. It was believed that the Krakatau easterlies layover the Berson
westerlies until 1954 when the transition was shown to vary year to year. In 1960 two scientist
independently discovered the QBO, R.J. Reed and R.A. Ebdon.
Reed used rawinsonde data from Canton Island (2.8°S) and observed “alternate bands of
easterly and westerly winds which originate above 30 km and move downward through the stratosphere
at a speed of 1 km per month.” He also noted that the bands appeared about every 13 months which
gave a total cycle time of 26 months. Ebdon used data from Canton Island as well to eventually show
that the period was between 25-27 months as well as using other site around the equator to show that
the changes happen simultaneously around the equatorial belt. Later it was determined that westerly
shear descend quicker and more frequently than easterly shears.
In 1986, Wallace and Holton figured out a way to get a QBO using upward propagating gravity
and other atmospheric waves, this model was later improved by Plumb in 1977.
(Baldwin et al, 2001)
Main Page Basic Model