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Summer 1998

La Niña summit set for July

by Bob Henson
UCAR Communications

As the 1997-98 El Niño limps along toward its expected demise, popular interest (fueled by scientists' statements) is swinging toward La Niña. It's too early to tell whether this cooling of the eastern tropical Pacific will arrive this winter, but an in-depth discussion of La Niña will hit Colorado this summer.

NCAR is playing host on 13-15 July to what is apparently the world's first meeting devoted to El Niño's less-studied counterpart. Called Review of the Causes and Consequences of Cold Events: A La Niña Summit, it is being organized by Michael Glantz (NCAR Environmental and Societal Impacts Group) with support from the United Nations University (UNU), which is based in Tokyo. The summit will draw a number of the nation's top researchers on La Niña and El Niño from universities and government agencies.

"To many people, anything that's not El Niño is considered normal," notes Glantz. La Niña is an enhancement of the normal sea-surface temperature pattern across the tropical Pacific (warm surface waters in the west and central Pacific, cool waters to the east). During La Niña, the easterly trade winds strengthen, cold upwelling off Peru and Ecuador intensifies, and sea surface temperatures there drop up to 3degreesC (7degreesF) below normal.

Unnamed until the mid-1980s, La Niña (Spanish for the little girl) has received less attention than El Niño. However, La Niña's effects--for instance, an increased hurricane threat in the Atlantic Ocean and Gulf of Mexico--can't be ignored. Another reason for the relative lack of attention: in the past 20 years there have been only three La Niñas, compared to seven El Niños, sparking some debate over whether global climate change might be tweaking the Pacific tropics toward a semipermanent warm state. (See the UCAR Quarterly, Winter 1997, for a look at El Niño and global warming.)

The summit is the first project in a "usable science" collaboration supported by UNU and aimed at helping Pacific Rim countries respond to El Niño and La Niña risks. Glantz is the project coordinator.

As for the El Niño now winding down, Glantz has compiled a summary of the predictions issued by 19 dynamical and statistical models between March 1996 and September 1997. Among the adjectives used to describe the El Niño then approaching: "strong," "weak," "quite weak," "quite strong," "warmish," "dropping to normal." Some models had caught on to the impending event by early 1997, while at least one missed it even as it was occurring. Ocean buoy data made it clear by summer 1997 that a major El Niño was in the works, and well-publicized forecasts created a media frenzy. Still, says Mickey, this event "developed earlier than expected, stayed strong longer than expected, grew bigger than expected, and was hotter than expected."

See the conference Web site and Glantz's article, "The El Niño Olympics, or The Search for the El Niño of the Century," .


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Edited by Carol Rasmussen, carolr@ucar.edu
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Last revised: Tue Apr 4 14:55:01 MDT 2000