Originally created 05/28/98

El Nino said to be lengthening the day, but not for long



BOSTON -- The days have been getting longer, and it isn't just a seasonal thing.

An extra one-tenth of a millisecond in your day is one of the few good things to come from El Nino, the warming trend that has been whipping up global weather problems.

That's right. The same phenomenon that produced torrential rains in Peru and drought in Indonesia is responsible for temporarily lengthening the days on Earth, according to a study released Tuesday at the American Geophysical Union's spring meeting in Boston.

David Salstein, a scientist with Cambridge-based Atmospheric and Environmental Research Inc., said El Nino stirred up westerly winds so much that the Earth had to slow its rotation in order to maintain stability with its surrounding atmosphere.

Salstein's findings are based on 15 years of data, much of it gathered by satellite.

The longest day resulting from this year's El Nino was Feb. 5, which was eight-tenths of a millisecond longer than normal, said John Gipson, one of Salstein's fellow researchers.

Klaus Weickmann, a meteorologist with the National Oceanic and Atmospheric Administration's Climate Diagnostic Center in Boulder, Colo., said El Nino's overall impact on day length was greatest last August through March, when the days averaged three- or four-tenths of a millisecond longer than normal.

Now they are about one-tenth of a millisecond longer than usual and soon will return to normal, he said.

"At this level it doesn't matter, but it's interesting scientifically," Gipson said.

It would matter, though, to space travelers.

Spacecraft such as the Mars Pathfinder use tracking devices on Earth to orient and navigate themselves in space, said Byron D. Tapley, a University of Texas researcher who participated in Tuesday's panel.

Part of that process is to figure out where the tracking devices are, a calculation that could be thrown off if the Earth is spinning at a different rate than expected.

In recent years, meteorologists have discovered that much of the year-to-year variation in the Earth's climate is controlled by El Nino, a warming of the Pacific waters off equatorial South America. It develops every few years and reaches a peak in November or December.

The current El Nino has been one of the most extreme in 50 or 100 years, Weickmann said.