The vertical structure of the quasi?biennial oscillation: Observations and theory

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Abstract
Rocketsonde observations of the zonal wind over Ascension Island (8°S) were analysed to obtain the amplitude and phase of the quasi‐biennial oscillation (QBO) in the height range 25–58 km. It was found that the amplitude peaked at about 30km and decreased rapidly above 40km. In fact, above 45 km there is no clear evidence that a QBO actually exists. A number of simulations using the Holton‐Lindzen model of the QBO were performed. It was found that when the waves in the model were damped with Dickinson's (1973) Newtonian cooling, the simulated QBO extended to higher levels than actually observed. However, when the wavelength‐dependent cooling rates of Fels(1981) were used, a fairly realistic vertical structure resulted.