Expansion of the Indo-Pacific warm pool and the Madden Julian Oscillation (MJO)

The Indo-Pacific warm pool—the region of permanently warm sea surface temperatures in the tropics—has been expanding at an accelerated rate during the recent decades. The talk summarizes the impact of the warm pool expansion on the most prominent element of subseasonal variability that travel across the tropics—the Madden Julian Oscillation. Our study shows that while the total lifespan of MJO remains the same during 1981-2018, its phase duration has decreased over the Indian Ocean by 3-4 days and increased over the Indo-Pacific Maritime Continent by 5–6 days in the recent two decades. We find that the impact of these changes are not limited to the tropics, and have a bearing on some of the severe weather events across the globe. As a response to the changes in the MJO phase duration, an increase in mean rainfall is observed over most of the Maritime Continent including southeast Asia, and over northern Australia, west Pacific, Amazon basin and southwest Africa. A decline in rainfall is observed over the central Pacific, Ecuador and California, and a slight decrease in rainfall over the Yangtze basin in China and Florida.