The Australian Bureau of Meteorology (http://www.bom.gov.au/climate/mjo, last access: 9 February 2023) states that "The Madden-Julian Oscillation (MJO) is a major fluctuation intropical weather on weekly to monthly timescale. The MJO can becharacterized as an eastward moving `pulse' of cloud and rainfall near theEquator that typically recurs every 30 to 60 days." Early descriptions ofthe MJO were contained in two papers by Madden and Julian (1971, 1972). This paper relates the story of developments in tropical meteorology in the 1960s that led to those two papers. The decade saw the first unambiguousidentification of large-scale, theoretically predicted, tropical waves. Spectral analysis was used effectively by researchers to link observationswith the theoretically expected features of these waves. At the same time,longer time series of observations, faster computers, and an algorithmdesigned to speed up Fourier transforms, vital for spectral analysis, allbecame available. These developments set the stage for the oscillation to be recognized.
