Southward Shift of Westerly Anomalies Around El Niño Decay Related to High‐Frequency Variabilities

Abstract The southward shift of anomalous westerlies from the equator to the south off‐equatorial areas plays a curtail role in demising El Niño, and was attributed to seasonal changes in the large‐scale environments in previous studies. Given that the southward shift exhibits a distinct spectral peak at the sub‐seasonal timescale, we propose that it could also be caused by the seasonal meridional movement of high‐frequency variabilities in the western tropical Pacific, such as the tropical cyclones (TCs) and Madden Julian Oscillation (MJO). It is found that the TCs and MJOs contribute to approximately 39% and 20% of the southward shift from October in El Niño years to the following March, respectively, both of which are significant at the 95% confidence level. Our findings supplement dynamics regarding to El Niño decay, and imply the necessity of improving seasonal forecast of high‐frequency variabilities for a better prediction of El Niño.