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Indian Ocean patterns to reveal onset of El Nino news
23 February 2010

Hong Kong: Climate scientists have announced the discovery of certain Indian Ocean climate patterns which they say could give up to 14 months' warning before the onset of an El Nino a weather anomaly that primarily impacts countries around the Pacific rim as well as southern Africa and at times even Europe.

Current templates allow scientists to provide no more than a few months' notice on the build-up of an El Nino. This is usually not sufficient for farmers, fishermen and others to prepare for severe disruptions in weather patterns that it brings.

El Nino heralds a major change in rainfall patterns, ushering in floods and mudslides in usually arid regions in western South America and drought in the western Pacific. It also alters patterns of nutrient-rich ocean currents that attract fish.

The El Nino phenomenon is cyclical, occurring every two to seven years, and is indicated when trade winds that circulate surface water in the tropical Pacific begin to weaken. This leads to the build up of a mass of warm water in the western Pacific which eventually transfers to the eastern side of the ocean.

Now, in a paper published in Nature Geoscience, meteorologists in Japan and France said a new forecast model built by them could predict the onset of an El Nino 14 months ahead of time, which would be well ahead of the warning period now available through current methods.

Meteorologists led by Takeshi Izumo of the Research Institute for Global Change in Yokohama, Japan, said their model would operate through early warnings received from a similar event that occurs in the Indian Ocean.

This oscillation, the so-called Indian Ocean Dipole (IOD), occurs roughly every two years. It was first identified in 1999.

Analysis of weather records in the period 1981-2009 found that when the IOD was in a "negative" phase that is waters were warm in the west and cold in the east -- an El Nino event in Pacific followed more than a year later.

"IOD strongly influences the triggering of El Nino (the following year). In this study, we did a simple forecast model, we included the IOD index and we can have a very good forecast for the El Nino in the next year," Izumo said.

"In a way we found a missing piece of the puzzle for triggering an El Nino. We showed here that in addition to the usual causal factor, which is that of warm water volume recharge, there is the IOD which is a very important causal factor for El Nino development," he added.

According to lead scientist, Izumo, this pendulum would appear to be set into motion by a pattern in atmospheric circulation which links both the oceans.

El Nino impacts nations and communities heavily dependent on agriculture and fishing. The 1997-1998 El Nino cost the United States an estimated $25 billion according to the US National Oceanic and Atmospheric Administration.

"Because of the overwhelming consequences of El Nino on global weather, ecosystems, and its strong socioeconomic and ecological consequences, El Nino forecasting is important for disaster prevention and impact management, and helps to reduce El Nino-related losses," Izumo said.

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Indian Ocean patterns to reveal onset of El Nino