The El Nino Climate Connection Meteorologists Analyze Effects of Pacific Ocean-Atmosphere Interaction on World Weather

Article excerpt

FLOODS in Texas. Typhoons in Japan. Warmer than normal surface temperatures across the central and eastern equatorial regions of the Pacific Ocean. It's the El Nino connection - or, to use a geophysical term, teleconnection.

The buildup of that equatorial warm-water pool over the past half year marks the return of the recurring phenomenon meteorologists call El Nino. It's a subtle trick the ocean-atmosphere system performs every two to 10 years that has worldwide weather impact. It has caught meteorologists around the world off guard in the past. This time, they were ready for it.

El Nino investigator James O'Brien at Florida State University in Tallahassee says El Nino research has accelerated since the last event faded out around 1987. This has yielded two important results: "A: we now can forecast it; B: we can specify its weather impacts better," he says.

This information can help affected regions prepare for El Nino-related weather changes. For example, with such forewarning, farmers in Peru, where El Nino brings heavy rains, could shift to rain-tolerant crops such as rice and avoid the catastrophic losses they used to suffer.

Perhaps the most significant result for meteorologists is that they now realize how seriously they have to take what once seemed a climatic curiosity. Climatologist Timothy Barnett of Scripps Institution of Oceanography in La Jolla, Calif., agrees that "what we've learned in the past five years is really incredible." He explains that the El Nino phenomenon now "looks like a normal mode of the coupled ocean-atmosphere system." He says, "It's the biggest short-term climate event on the planet, and it affects billions of people."

Dr. Barnett points out, for example, that the atmospheric circulation that locked in over North America this winter "is kind of a classical El Nino pattern" with a high-pressure ridge in the West and a low-pressure trough in the East. That's a long way from the equatorial Pacific. But the tie-in seems clear.

Climate investigator Kevin Trenberth at the National Center for Atmospheric Research (NCAR) in Boulder, Colo., agrees: "The fact that storms have penetrated that far south {into Texas} and linked up with moisture sources to cause intense flooding is consistent with an El Nino circulation pattern."

Meanwhile, Japan experienced several times the normal number of typhoons last year. The Japan Meteorological Office has blamed this on El Nino too.

Dr. O'Brien says he finds that plausible. As an El Nino condition develops, sea-surface temperatures cool in the Western Pacific and rise in central and eastern tropical regions. The result is a greatly expanded area of above-average sea surface temperatures. …

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