fundamental advance in the field of tropical meteorology was the discovery by Madden and Julian (1972) that the dominant compo-nent of intraseasonal variability in the tropics is a rainfall, now known as the Madden–Julian oscillation (MJO). Nakazawa (1988) suggested that these tropi-cal intraseasonal oscillations are actually space–time envelopes of multiple organized clusters and super-clusters of convective clouds occurring on shorter scales than the longwave oscillation. While the MJO envelope propagates eastward, the embedded clus-ters and superclusters move at faster speeds in both directions. Recent studies (e.g., Wheeler and Kiladis 1999), using outgoing longwave radiation (OLR) spectrum power to produce empirical estimates of the frequency–wavenumber structure of propagating features, have identified these clusters and superclus-ters as the moist equivalents of linear shallow-water equatorially trapped waves, whereas the MJO signal appears on the bottom of the empirical dispersion diagram, separate from the dispersion relation curves of the linear waves. Organized convection and convectively coupled waves in the tropics have a sig-nificant impact on midlatitude weather and climate through atmospheric and oceanic teleconnection patterns (e.g., Zhang 2005). While a broad range of mechanisms has been proposed to explain the MJO, it is typically only poorly represented in contemporary general circulation models (GCMs), apparently due to the inadequate treatment across multiple spatial scales of the interaction of the associated hierarchy of organized structures.