A pioneering time of discoveries in large-scale tropical meteorology: 1960 through 1972

Abstract. 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 in tropical weather on weekly to monthly timescale. The MJO can be characterized as an eastward moving `pulse' of cloud and rainfall near the Equator that typically recurs every 30 to 60 days.” Early descriptions of the 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 unambiguous identification of large-scale, theoretically predicted, tropical waves. Spectral analysis was used effectively by researchers to link observations with the theoretically expected features of these waves. At the same time, longer time series of observations, faster computers, and an algorithm designed to speed up Fourier transforms, vital for spectral analysis, all became available. These developments set the stage for the oscillation to be recognized.