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An international research team has found how a major fluctuation in tropical weather — the Madden–Julian Oscillation (MJO) — is shaped by the increased warming of the tropical oceans1. The findings could help better understand the MJO, which each year adversely affects human life and the global economy.
The MJO moves eastwards along the Equator, drastically influencing the formation of clouds, rainfall, winds and pressure. It even modulates tropical cyclones and monsoons, contributing to severe weather events over Asia, Australia, Africa, Europe and the Americas. However, it is still unclear how the MJO gains strength and unleashes such devastating effects.
The researchers, including scientists from the Indian Institute of Tropical Meteorology in Pune and Andhra University in Andhra Pradesh, have shown that rapid warming over the tropical oceans during 1981–2018 distorted the MJO life cycle. This decreased the oscillation's residing time over the Indian Ocean by 3–4 days, and increased it over the Indo-Pacific Maritime Continent by 5–6 days.
Such changes in the MJO life cycle have been linked to a two-fold expansion of the Indo-Pacific warm pool, the largest expanse of the warmest ocean temperatures on Earth.
The changes in the warm pool and the MJO probably lead to increased rainfall over south-east Asia, northern Australia, south-west Africa and the Amazon, and drying over the west coast of the United States and Ecuador.
The researchers say that further increases in ocean temperature, particularly in the warm pool, may intensify the changes in the MJO life cycle in future.
References
1. Roxy, M. K. et al. Two-fold expansion of the Indo-Pacific warm pool warps the MJO life cycle. Nature. 575, 647–651 (2019)
