Zonal phase propagation of ENSO sea surface temperature anomalies: Revisited



[1] Previous studies have identified a reversal in the phase propagation characteristics (from westward to eastward propagation) of the El Niño–Southern Oscillation (ENSO) during the 1976 climate shift. These studies relied on the assumption of a stationary seasonal cycle in Sea Surface Temperature (SST), ignoring the possible effect of ENSO and decadal variability on the seasonal cycle strength. Here we demonstrate using complex empirical orthogonal functions combined with Radon transform methods that mutidecadal amplitude modulations of the seasonal cycle, the semiannual cycle, and the El Niño Modoki mode played an important role in determining the phase propagation characteristics of equatorial SST anomalies in past decades. We find very little evidence for changes in the propagation characteristics of the Cold Tongue ENSO mode.