Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: TUESDAY, August 9, 1994 TAG: 9408090089
SECTION: NATIONAL/INTERNATIONAL PAGE: B5 EDITION: METRO
SOURCE: NEW YORK TIMES
DATELINE: LENGTH: Medium
Warm sea-surface temperatures in the Pacific, and especially those associated with El Nino, are known to set off chains of atmospheric events that dictate the weather in many parts of the world, including North America.
But it generally has been assumed that once the sea temperatures around the equator return to normal after one to three years, El Nino's influence is over.
Now, a study suggests that El Nino of 1982-83 still may be exercising its climatic powers. The study was based on satellite tracking of large-scale movements of warm ocean water initiated by that El Nino, the strongest such event in this century.
The study found that a characteristically large wave of eastward-moving warm water associated with the 1982-83 El Nino glanced off the American land mass and rebounded northwestward across the Pacific, carrying large amounts of heat with it and raising the temperatures of parts of the Pacific even today.
The study, by Gregg A. Jacobs, an oceanographer at the Naval Research Laboratory at the Stennis Space Center near Bay St.Louis, Miss., and six colleagues, is reported in the current issue of the British journal Nature.
Since the amount and location of warm water in the Pacific have much to do with the births and wanderings of storm systems, the finding could complicate the already daunting task of climatologists who are attempting to understand the causes of the last decade's unusual run of extreme weather around the world.
``This is opening up a whole new can of worms,'' said Daniel J. Leathers, a climatologist at the University of Delaware who has studied the link between Pacific sea-surface temperatures and weather patterns in North America.
The lingering effects of the 1982-83 warming caused by El Nino have been superimposed not only on two later and less intense El Ninos in 1986-87 and 1991-93, but also on all other fluctuations in Pacific temperature in the last 11 years. El Nino appears every two to seven years.
The oceans, and especially the Pacific, exert a powerful effect on world climate through the mass transport of heat and the evaporation of water. The water vapor condenses to form storm clouds, releasing latent heat into the atmosphere in the process.
This provides the atmosphere's largest single heat source, and the higher the ocean temperature in a location, the greater the production of water vapor, clouds and atmospheric heat. The climate system's complex internal linkages, only partly understood by scientists, determine how the clouds and heat are distributed around the globe.
In a vivid demonstration of El Nino's long reach, scientists reported last month that the comings and goings of the phenomenon are reliable predictors of rainfall and corn yields in southern Africa.
El Nino starts when, through causes not well understood by scientists, prevailing easterly winds slacken at the equator, allowing a broad but subtle wave of warm water from the western Pacific to flow eastward toward South America.
by CNB