Tutorial 2

Laboratory analogue of the quasi-biennial oscillation (QBO)

The quasi-biennial oscillation (QBO) is a large-scale, roughly cyclic oscillation of the zonal (east–west) wind in the Earth's equatorial stratosphere, with an approximate period of around two years. It has been observed since the 1950s, and is widely understood to arise from the interaction between upward-propagating waves, generated in the troposphere, and the mean zonal flow at upper levels where the waves are dissipated. The basic mechanism was beautifully illustrated and verified in the laboratory in the late 1970s by Alan Plumb and Alastair McEwan, working at CSIRO in Australia. Here we provide a brief introduction to the QBO in the Earth's stratosphere, and present an outline of Plumb and McEwan's original experiment, together with some movies showing some of their remarkable results.


The following pages provide an outline of the theory behind the QBO, and a way of simulating the effect in the laboratory, with clips from the original experiment behind the seminal research paper verifying that the theory works:

2.1. Introduction

2.2. Description of experimental apparatus

2.3. Experimental results