SUNLIGHT, SUN BRIGHT -- Sandia's Larry Yellowhorse examines an instrument that measures sunlight intensity. The sensor is part of a Sandia-built Atmospheric Radiation and Cloud Station that will spend the next 10 years on the tiny Pacific island of Nauru gathering data about how sunlight and infrared radiation interact with clouds, which may help scientists predict global climate change and better understand weather phenomena such as El Niño and La Niña. (Photo by Randy Montoya) Download 150dpi JPEG image, 'SolarYH.jpg', 878K

Weather on remote Pacific island may hold clues to possible global climate change

ALBUQUERQUE, N.M. -- A team of researchers from the U.S. Department of Energy's national laboratories in New Mexico traveled 6,500 miles recently to a remote Pacific island to better understand, in part, why the American Southwest is having such a warm, dry winter and why the Great Lakes states are getting so much snow.

The scientists took with them an atmospheric measurement station built and tested at Sandia National Laboratories in Albuquerque. The station, called an Atmospheric Radiation and Cloud Station (ARCS), is now gathering information about clouds and sunlight from the tiny Pacific island of Nauru 1,800 miles northeast of Australia. The cloud-watching station will operate on Nauru for at least 10 years.

Clouds can reflect incoming sunlight and contribute to cooling. They also can absorb radiation leaving Earth's surface and contribute to warming. Scientists suspect that atmospheric moisture may amplify global warming effects as well. But with little scientific data about these interactions, researchers can't verify whether Earth is experiencing a temporary hiccup in global temperatures or is undergoing a gradual, global warming trend. The measurement station will help scientists study this uncertainty.

In addition, the tropical western Pacific region where the new station is located is thought to play a critical role in the periodic El Niño and La Niña weather phenomena. Meteorologists generally blamed El Niño, which occurs every two to seven years, for unusually wet weather across much of the Northern Hemisphere in late 1997 and most of 1998. La Niña, a weather pattern that typically follows El Niño, is characterized by warm, dry winter weather in the West and Southwest, harsher than normal conditions in the Midwest, and enhanced hurricane activity in the mid-Atlantic states.

Although scientists agree that we are now experiencing La Niña, the climatic factors that give rise to this weather phenomena, and to El Niño, are not yet well understood.

Convenient 'warm pool' locale
Installing an ARCS station on Nauru is a milestone in a larger Department of Energy (DOE) program that seeks to understand how sunlight and infrared radiation interact with clouds and, in particular, whether varying levels of atmospheric moisture could permanently influence Earth's heat budget.

The Atmospheric Radiation Measurement (ARM) program's goal is to establish groupings of atmospheric measurement stations in three regions of the world where weather mechanisms are thought to play critical or not-yet-well-understood roles in the overall climate picture. The U.S. Southern Great Plains site in Oklahoma and Texas became the first active ARM region in 1992. Stations in ARM's North Slope of Alaska region began operating last summer.

The Nauru station is the second ARCS now operating in the tropical western Pacific region. The first Pacific station began operating in 1996 on Manus Island, Papua New Guinea. Sandia engineers are building a third ARCS scheduled to be placed in the region next year.

The Nauru locale is particularly significant because the island is situated on the edge of what climatologists call the "warm pool." The region's unusually warm ocean waters act as a sort of cloud factory, supplying heat and moisture to the atmosphere above, resulting in formation of high-altitude clouds that disperse over the entire region.

In an El Niño, unusually weak west-moving trade winds allow these warm surface waters to slosh eastward toward the Americas, altering world precipitation patterns. In a La Niña, stronger trade winds blow this warm pool toward Indonesia. In the U.S., the resulting shift in jet stream patterns means some snow-laden winter storms can miss the Rocky Mountain states and dump on the Great Lakes region, for instance.

By watching a decade of weather develop from the edge of the warm pool, says Sandia integration manager Mark Ivey, researchers hope to shed light on the role of clouds in these phenomena.

"We'll study clouds as they form, watch how storms develop, and observe climate changes as the warm pool shifts," he says.

Atmospheric info for global climate models
For the next 10 years, the station's instruments will collect data on such climate indicators as incoming solar energy, ground-reflected radiant energy, atmospheric energy absorption, cloud height and density, cloud cover, temperature, and wind direction and speed. Two weather balloons per day are launched and tracked automatically.

The station will gather more than a gigabyte of data a day, most of which will be sent back to the U.S. on magnetic tape. Three islanders have been hired to monitor and maintain the station. ARM program engineers will visit the island periodically.

A DOE team is scheduled to return to Nauru this summer as part of a related experiment called Nauru '99, during which researchers using ship-borne instruments will try to measure the effects of the island land mass on cloud formation and movement.

Data gathered as part of the ARM program are expected to be fed into computer programs that simulate global climate, called general circulation models. These models may one day help researchers and policymakers better understand the mechanisms that affect Earth's climate and determine whether it is undergoing a systematic warming triggered by emissions of manmade "greenhouse" gases.

Los Alamos National Laboratory, which manages ARM's Tropical Western Pacific Program Office for DOE, selected Sandia to integrate, develop, and test ARCS stations for the TWP region. Sandia also manages ARM's North Slope of Alaska Program Office and built the ARCS stations for that region as well. Argonne National Laboratory manages the Southern Great Plains site, and Pacific Northwest National Laboratory coordinates the overall ARM program for DOE. More information about the ARM program can be found at http://www.arm.gov/.

Sandia is a multiprogram Department of Energy laboratory operated by Lockheed Martin Corporation. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has R&D programs contributing to national defense, energy and environmental technologies, and economic competitiveness.

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