El Nino was every weatherman’s favorite scapegoat in 1998, taking the blame for eight months of meteorological mayhem across much of the Northern Hemisphere. But for those trying to forecast the weather beyond the middle of next week, El Nino is at least an accessory in the greatest climate caper of all.

A group of Labs engineers has built and tested an atmospheric measurement station that is helping a multi-lab DOE research team study not only El Nino’s seasonal influence on the weather, but also the likelihood that Earth is undergoing long-term global climate change. Late last month the Sandia-integrated Atmospheric Radiation and Cloud Station (ARCS) began gathering atmospheric data from the tiny Pacific island of Nauru about 1,300 miles northwest of Papua New Guinea.

Installing an ARCS station on Nauru is a milestone in DOE’s Atmospheric Radiation Measurement (ARM) program, which 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 radiative heat budget.

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 high levels of atmospheric moisture may amplify global warming effects as well.

Convenient ‘warm pool’ locale

The 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 US Southern Great Plains site became the first active ARM region in 1992. Stations in ARM’s North Slope of Alaska region began operating last summer (Lab News, Aug. 1, 1997).

The Nauru station — dedicated Nov. 20 on the island’s western shore — is the second ARCS now operating in the tropical western Pacific (TWP) region. The first began operating in 1996 on Manus island, Papua New Guinea. A third station in the TWP region is planned for the island of Kiritimati (a.k.a. Christmas Island) in the year 2000.

The Nauru locale is particularly significant because the island is situated on the eastern 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.

Every two-to-seven years, however, unusually weak westerly trade winds allow warm equatorial surface waters to slosh eastward toward the Americas, shifting precipitation patterns and giving rise to the El Nino-Southern Oscillation phenomenon that is thought to have far-reaching implications for weather patterns over much of the Northern Hemisphere and perhaps the planet.

By situating an ARCS station on the edge of the warm pool, says ARCS integration manager Mark Ivey (6233), ARM researchers hope to shed light on the role of clouds in this phenomenon. "We may be able to study clouds as they form, watch how storms develop, and observe changes in climate-related mechanisms as the warm pool shifts," he says.

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 US on magnetic tape. Three islanders have been hired to monitor and maintain the station. ARM program engineers will visit the island periodically. Like being on the open sea

The ARCS was integrated at Sandia/New Mexico and then shipped to Nauru this summer. From August to November about 25 people, including eight Sandians, rotated to and from Nauru preparing the ARCS for operations.

Because of the heat and humidity and the heavy workload, the tour of duty on Nauru wasn’t quite a junket, Mark says, but working 30 feet from a sandy shore had its perks. Some team members took advantage of the island’s deep-sea fishing opportunities. A wild pig that visited daily became the site’s mascot and much of its entertainment.

He says taking measurements from such a small island — it’s only about 5 km in diameter — minimizes the effects of the land mass on the atmosphere above. "It’s the closest thing to being on the open ocean," he says.

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 on cloud formation and movement.

Data gathered as part of the overall ARM program are expected to be fed into improved general circulation models that 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.

Sandia was selected as the technical lead for integrating, developing, and testing all three ARCS stations for the TWP region by Los Alamos National Laboratory, which manages ARM’s Tropical Western Pacific Program Office. Sandia manages ARM’s North Slope of Alaska/Adjacent Arctic Ocean Program Office and integrated the ARCS for that region as well. Pacific Northwest National Laboratory manages the overall ARM program for DOE.