 Monsoon approaches India (NASA) |
Indian Ocean Dipole rains on ENSO’s influence03 August 2011 The Indian Ocean may play a major role in modulating the effect of the Pacific Ocean’s El Niño Southern Oscillation (ENSO) on the Indian monsoon, according to a new paper by CCRC researchers. The paper, Multi-Decadal modulation of El Niño-Indian monsoon relationship by Indian Ocean Variability, has highlighted how the Indian Ocean Dipole (IOD) appears to have a high level of influence over India’s monsoon season on decadal timescales. It is well known that the Indian monsoon often fails during El Nino events, bringing drought to the region. Recent work has also shown that this failure does not happen if the Indian Ocean is in a certain state, called a ‘positive IOD’. A new study by researchers at the CCRC has found that these relationships can be used to explain the reduction in droughts that has occurred in recent decades. “What we have found is that this mechanism is not only at play during year-to-year variations in the Indian monsoon but it can also explain a weakening in the relationship between ENSO and the Indian monsoon during recent decades,” said lead author, Dr Ummenhofer. “This research indicates that we need a more nuanced view of the relationship between the Indian Ocean and the Pacific ENSO than previously believed.” Dr Ummenhofer’s research looked at 130 years of data, showing the effect of the IOD over multi-decadal timescales. Broadly, the data indicated that:
Based on these findings, the recent weakening of the El Niño effect on the Indian monsoon from 1975-2006 can be explained in large part by the fact that many El Niños during this period occurred along side a positive IOD. The higher frequency of this combination appeared to support successful Indian monsoons. It also contributed to drier conditions across south-east Australia. “This early research reinforces that we need to focus more resources on studying the Indian Ocean if we are to understand the climate patterns in Australia, India and South East Asia in the future,” Dr Ummenhofer said. “We urgently need to determine how climate change is affecting the frequency and nature of the IOD and, if so, what this means for future rainfall patterns around agricultural regions in Australia and across Asia. The project is part of new Australian Research Council funded research: The changing relationship between the South Asian and Australian Monsoon in a warming world. The project was awarded to Alex Sen Gupta, Matthew England, Andrea Taschetto, Caroline Ummenhofer, together with three collaborators at the Indian Institute of Tropical Meteorology, Karumuri Ashok, Raghavan Krishnan and Sahai Atul. The research is of great importance to Australia’s future as tropical monsoonal systems have enormous social, economic and environmental impact across the north of Australia and the wider South Asian region. The success or failure of the Australian and South Asian Monsoons can mean the difference between prosperity and severe hardship in the affected regions. This project will help to understand the causes of the monsoon variability, both natural and human-induced, and what the future might have in store. This paper has just appeared as a research highlight in Nature Climate Change. Links:
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