The Hindu Business Line : New model for tracking El Nino

A UNIQUE statistical model forecasting sea surface temperatures in the tropical Pacific is projected as being able to forecast El Nino phenomenon six months in advance — long enough for farmers, commercial fishermen and even insurers to plan for the coming season.

El Nino is a term used to represent anomalously high sea surface temperatures (SST) in the east equatorial Pacific. These high SSTs are caused by reduced upwelling in the east equatorial Pacific due to lighter easterly trade winds.

Normally, temperatures of surface waters in the western Pacific are 6 to 8 degrees Celsius (10 to 15 degrees Fahrenheit) warmer than in the east. But during an El Niño, the temperature differential reverses.

El Niño causes far-reaching weather events, including drought and heatwaves across Australia, torrential rainfall in Central and South America, and heavy winter snows and floods in the southern US — all of which affect water resources and food supply. Closer home, El Nino's influence on the Indian summer monsoon has been a hot subject of debate among meteorologists and scientists.

The uniqueness of the new model developed by the Ohio State University flows largely from the in-built "measures of uncertainty" surrounding this climatic condition. Such measures are important for quantifying risk when, for example, farmers and insurance companies make decisions about the next harvest, according to Prof. Noel Cressie, Professor of Statistics and Director of Programme in Spatial Statistics and Environmental Sciences, Ohio State University.

The model gives scientists a way to quantify the uncertainty that surrounds El Niño. It represents a new paradigm in geophysical modelling, where all sources of uncertainties are accounted for in melding of geophysical knowledge and statistical description, according to Prof. Cressie.

In this case, the strength of westerly winds in a particular location of the tropical Pacific is a key component. Although the research team discovered this relationship through their own exploratory spatial data analysis, this experimental finding fits with one dominant scientific paradigm that westerly wind bursts are an important factor in the pooling of warm surface waters in the eastern Pacific.

For the first time, a tool based on the model is available on the Web (http:// www.stat.ohio-state.edu/sses/collab_enso.php). Animations of El Niño forecasts from January 1985 through May 2004 can be viewed.

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