Sandia LabNews

ARM-UAV program hosts planning for expedition

ARM-UAV program hosts planning for expedition

Years of aspirations to undertake challenging climate research materialized recently in a core group of weather scientists from the US, Europe, and Australia gathering at Sandia/California to discuss upcoming plans for observations of the atmosphere above the western tropical Pacific, a region known as the world’s climate engine.

The studies in January-February 2006 will focus on the key uncertainty in climate modeling, the role of clouds, which can either trap or reflect heat from the sun. The formal name is the Tropical Warm Pool-International Cloud Experiment.

“The tropics are very important to global climate,” said Will Bolton (8227), who manages DOE’s Atmospheric Radiation Measurement – Unmanned Aerospace Vehicle (ARM-UAV) Program at Sandia and hosted the planning session. “What goes on there affects climate virtually all over the world.”

Deployment coincides with monsoon season

The deployment coincides with monsoon season around Darwin, Australia, which was instrumented three years ago to gather ground-based measurements for the ARM program.

“We’ve always wanted to do this type of experiment,” said Jim Mather, a meteorologist with Pacific Northwest National Laboratory who co-leads the science team for the western tropical region. “We’ve been working on this for years. It’s a very difficult experiment to do.”

Will said the three days of planning in Livermore in September were intended to improve efficiency when the team collects data in Australia. Using satellite and weather radar images, Bureau of Meteorology forecasts, and weather prediction model runs from the same period last year, the team ran through a speeded-up day, deciding flight paths for the following day and then checking what weather conditions prevailed and how the choices might have worked out.

Dry run ‘extremely useful’

Mather called the dry run “extremely useful,” saying, “we’re really learning quite a lot about how this process flows.” Altogether, the group expects about 50 hours of aircraft time from each of five planes, flying under, above, and through the clouds at altitudes of 15,000 to 50,000 feet.

Measurements will be taken using instruments not only on the aircraft, but also on the ground, on a ship, by satellite, and by weather balloons — more than 1,000 of which will be launched in a ring around the study area during the three-week study period.

Mather expects the data gathered over three weeks to be used for the next decade in improving climate models. Will said the improved understanding can eventually be applied to weather forecasting as well as predicting longer-term climate change.

In addition to the roughly 20 scientists who gathered in Livermore, the deployment will involve about 200 other participants, said Peter May, a researcher with the Australian Bureau of Meteorology who helped organize the meeting. Major funding comes from the DOE, NASA, Australia, and the United Kingdom.

This is the third and final stop in a “grand tour” of ARM-UAV airborne experiments at ARM sites worldwide. The first series of flights was conducted over north-central Oklahoma in 2002, and the second over the North Slope of Alaska in October 2004.

The tropical western Pacific site, only some 700 miles south of the equator, has the largest “solar input,” Mather said, and features massive shields of high-altitude cirrus clouds that spread for thousands of miles, exerting an even larger effect on climate and weather than the thunderstorms that precede their formation.

“They’re difficult to get to,” Mather said. “Some of these aircraft are fairly exotic.” The Egrett and Proteus high-altitude aircraft will be joined by the lower-flying Twin Otter, Dornier, and Dimona planes.

The UAV program uses both piloted and unpiloted aircraft to measure physical properties of clouds as a function of height and time. The knowledge gained can inform political or economic decisions, such as those governing use of fossil fuel, that influence climate change.

Experiment participants come from government and university research groups in Australia, Canada, Europe, Japan, and the US.