A Secular Shift of the Madden-Julian Oscillation and Its Relation to Western Pacific Ocean Warming

Abstract

In the context of global warming, understanding changes in the Madden-Julian Oscillation (MJO) is of great importance, because of its worldwide impact on surface weather and climate. By analyzing the temporal evolution of the phase relationship between Kelvin waves and the MJO, we find a secular phase shift of the MJO after year 2000, at which the MJO exhibits an eastward extension over the Maritime Continent and the Western Pacific Ocean. Further, we examine the influence of sea surface temperature (SST) variations on the anomalous convection and Kelvin waves, and demonstrate that the recent warming trend of the Western Pacific SST is a factor causing the changes of the MJO over this region. The results deepen our understanding of recent modeling and observational studies about the changes of the MJO and confirm the enhanced activity of the MJO over the past few decades.