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Climate Researchers Focus on Tropical Pacific,‘Driver' of Global Weather

The Tropical Western Pacific serves as the earth's heat engine, driving global weather events such as El Niño and La Niña, but this "furnace" is poorly understood. Scientists, hoping to gain a better understanding of this key area in worldwide climate, converged on the small island republic of Nauru this summer for a one-month field program. Their hope was to discover more about how the Earth's atmosphere and climate are affected by the tropics.

From mid-June to mid-July, Nauru and its surrounding waters hosted the most complete suite of atmospheric instrumentation ever installed in the Tropical Western Pacific. Included was the Ronald H. Brown, a large research vessel, aircraft , buoys and research balloons, all equipped with specialized instrumentation to gather a variety of atmospheric data.

Nauru99 is sponsored by the Department of Energy's Atmospheric Radiation Measurement (ARM) Program and was conducted in partnership with NOAA's Environmental Technology Laboratory, the Japan Marine Science and Technology Center (JAMSTEC), Australia's Flinders University and several American universities.

Of particular interest to campaign participants is the energy flux, or transfer of energy, that occurs between the ocean and atmosphere. Scientists are studying how radiative energy enters and exits the ocean surface, and how clouds affect this transfer.

"These energy fluxes are the primary means by which the ocean impacts our atmosphere," said Tom Ackerman, chief scientist for the ARM program. "A better understanding of these mechanisms will provide valuable insights into how the tropical ocean impacts weather and climate around the globe."

According to Ackerman, the bulk of information on ocean-atmosphere energy fluxes stems from relatively short-term ship and aircraft experiments. To supplement this, the ARM program launched an effort in 1997 to obtain long-term, land-based measurements through installation of major facilities on Manus Island in Papua New Guinea, and most recently on Nauru. These measurements focus on downwelling, or the downward direction, of radiative energy from the atmosphere and the effect of clouds on this energy.

Nauru Cloud and Radiation Testbed (CART) Site

Island-based measurements are cheaper and logistically easier to obtain than ship-based measurements and provide the only opportunity for multi-year observations. Scientists, however, must identify and adjust for the influence of the landmass on these measurements.

"Nauru99 is the first comprehensive experiment to determine whether land-based measurements serve as effective surrogates for ocean measurements and, therefore, how well these measurements can be used to develop more reliable climate models," said M. J. Post, chief scientist for the Ron Brown and Chief of the System Demonstration and Integration Division (SDID), within the Environmental Technology Laboratory.

Begun in late June, the campaign focused on detailed comparisons of island-and ocean-based measurements. Configured in a triangle approximately 360 miles in circumference, the three primary data collection points will consist of NOAA's Ron Brown research vessel, JAMSTEC's Mirai and ARM's instrumentation installation on Nauru. The configuration enables scientists to simultaneously collect and compare data from both ships, the island and the more than 70 NOAA instrumentation buoys currently anchored throughout the tropical ocean.

The field portion of the campaign concluded July 17. Initial data analyzed by individual scientists will be integrated to provide a clearer picture of ocean-atmosphere interaction and island effects. Final results of the campaign will be released early next year, although some preliminary results may be released this fall. Scientists expect data collected in Nauru99 to be used for scientific investigations over the next decade.

For more information on Nauru99, including photos, updates and a detailed science plan, please see the Nauru99 web site at: http://www.arm.gov/docs/news/nauru99 or the NOAA/ETL web site at http://www.etl.noaa.gov/nauru99/

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