Tripling of MJO residence time over the rapidly warming Indian Ocean during summer monsoon

Abstract

The Madden-Julian Oscillation (MJO) is the dominant mode of intraseasonal tropical atmospheric variability with far-reaching influences on global weather systems. During boreal winter, the MJO typically exhibits regular eastward propagation, whereas in summer, it displays more complex propagation characteristics, such as frequent stalling over the Indian Ocean. Here we show a threefold increase in the MJO residence time over the Indian Ocean during the Asian summer monsoon in recent four decades. This drastic increase is closely associated with the rapid warming of the Indian Ocean, which contributes to increased extreme climate events across Indian Ocean rim countries. This peculiar warming pattern is projected to persist under anthropogenic warming, potentially facilitating prolonged MJO activity over the Indian Ocean with higher climatic disaster risks in the future.