Scientists see early warning to damaging El Nino

Yahoo News 21 Feb 10;

PARIS (AFP) – Weather experts say they have a tip that could give up to 14 months' warning before the onset of an El Nino, the weather anomaly that whacks countries around the Pacific and affects southern Africa and even Europe.

At present, scientists are unable to give little more than a few months' notice that an El Nino is in the offing, which is often too late for farmers, fishermen and others to prepare for weather disruption.

El Nino occurs every two to seven years, when the trade winds that circulate surface water in the tropical Pacific start to weaken.

A mass of warm water builds in the western Pacific and eventually rides over to the eastern side of the ocean.

The outcome is a major shift in rainfall, bringing floods and mudslides to usually arid countries in western south America and drought in the western Pacific, as well as a change in nutrient-rich ocean currents that lure fish.

El Nino is ushered out by a cold phase, La Nina, which usually occurs the following year.

Meteorologists led by Takeshi Izumo of the Research Institute for Global Change in Yokohama, Japan, believe the world can gain a precious early warning from a similar event that occurs in the Indian Ocean.

This oscillation, first identified in 1999, occurs roughly every two years.

Analysis of weather records from 1981 to 2009 found that when the so-called Indian Ocean Dipole was in a "negative" phase -- with the waters warm in the west and cold in the east -- an El Nino event in Pacific followed more than a year later.

The driver for this pendulum appears to be a pattern in atmospheric circulation linking the two oceans, Izumo believes.

The paper is published online on Sunday by the journal Nature Geoscience.

In a commentary, Peter Webster and Carlos Hoyos, earth scientists at the Georgia Institute of Technology, Atlanta, said that work was needed to delve into the past.

The 1981-2009 period did indeed show a "strong two-year rhythm" in which the Dipole swung along with El Nino.

Other research, based on sea temperatures from 1890-2008, suggests the Indian Ocean pendulum may vary from decade to decade, the pair cautioned.

Indian Ocean Clues To Predicting El Nino: Study
Tan Ee Lyn, PlanetArk 24 Feb 10;

HONG KONG - Tracking Indian Ocean climate patterns could improve early-warning systems for the El Nino phenomenon, helping save lives and billions of dollars lost each year to the severe weather it causes.

In a paper published in Nature Geoscience, researchers in Japan and France said their new forecast model could predict an El Nino 14 months ahead of time, several months earlier than with current methods.

"It is important because...this helps to improve El Nino forecasts. It can save a lot of money for agriculture," lead researcher Takeshi Izumo at the Research Institute for Global Change in Yokohama, Japan, said by telephone.

The El Nino phenomenon is a climate pattern that occurs periodically over the Pacific Ocean and is well known for the havoc it wreaks such as floods, droughts and other forms of severe weather.

Developing countries heavily dependent on agriculture and fishing are most badly affected, though the 1997-1998 El Nino cost the United States an estimated $25 billion according to the US National Oceanic and Atmospheric Administration.

Izumo and his colleagues found that the Indian Ocean Dipole (IOD), the equivalent of an El Nino in the Indian Ocean, had a role in causing the phenomenon.

"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.

Accurate and early prediction of the El Nino can help better mitigate the destruction caused by the phenomenon.

"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.

During the 1997 El Nino, one of the strongest recorded, Indonesia suffered a large number of fires, partly caused by drought, he said. Better forecasting could have helped reduce the number of fires through prevention measures.

(Editing by Jon Boyle)