Sandia LabNews

ARM-UAV program makes it to the arctic for first time

ARM-UAV program makes it to the arctic for first time

A dozen years after it got off the ground, DOE’s Atmospheric Radiation Measurement – Unmanned Aerospace Vehicle (ARM-UAV) Program carried out a series of high-altitude research flights in the arctic region for the first time in its history, with three weeks of climate change measurement flights over the North Slope of Alaska in October 2004.

The flights were the subject of talks this month in Daytona Beach, Fla., where ARM scientists gathered to discuss that mission along with a broad range of climate-related measurement campaigns. Another topic of discussion was the upcoming February 2006 ARM-UAV deployment to Darwin, Australia, where the airborne data-gathering instruments will be used in conjunction with ground-based, satellite, and ship-based instruments to collect information about the characteristics of tropical clouds at altitudes up to about 50,000 feet above the tropical Western Pacific.

Second stop of a ‘grand tour’

The Alaska flights were the second stop in a “Grand Tour” above ARM climate research sites to answer unsolved issues about the interaction of clouds and solar energy. The improved understanding that will come from these measurements will help improve predictive climate models.

The first series of flights was conducted over north-central Oklahoma in 2002. The third stop in the “Grand Tour” will be in Australia.

The conundrum about clouds is whether they tend to shade and cool the Earth or blanket it, trapping in heat and raising the surface temperature, says Exploratory Systems Technology Dept. 8227 Manager Will Bolton, who is technical director for the program.

To understand their role better, a piloted Proteus aircraft was outfitted with 15 discrete instruments, some mounted on the wings, others carried in a payload pod carried under the aircraft or atop the fuselage. Proteus was built by and is operated by Scaled Composites, in Mojave, Calif. The plane underwent three engineering flights there while the payload was controlled through a low-cost satellite link. Then it was flown up to Alaska, refueling in Seattle, with the payload controlled from up to 2,000 miles away through the satellite link.

From Eielson Air Force Base near Fairbanks, the Proteus flew about 90 minutes to the North Slope, rendezvousing with a Citation aircraft provided by the University of North Dakota that was stationed at Dead Horse, Alaska. With the Proteus flying up to 13 kilometers in altitude and the Citation flying inside the clouds, the planes collected data in flights lasting from 96 minutes to almost six hours. It will take about six months to process and calibrate the data, which is stored in the ARM archive based at Oak Ridge National Laboratory as a public resource available to scientists and universities.

Helping understand cloud physics

The data gathered by the ARM-UAV Program will help guide the way in which cloud physics is embodied in climate models. The models currently differ substantially in how they represent clouds and their effects on the atmosphere.

Whenever possible, the ARM-UAV flights are coordinated with satellite overflights of the ground stations. The coincidence of aircraft-borne and satellite measurements over the ground-based instruments provides a more complete picture of cloud characteristics and offers the advantage of comparing the satellite data with data from more recently calibrated instruments.

Sandia’s mission support includes calibrating the instruments, building or modifying some, handing mechanical and engineering design and integration with the aircraft, coordinating field arrangements such as planning and logistics, retrieving and processing data, and directing flight operations at the deployment site.

The latest deployment was supported by some 15 people from universities, laboratories, and industry, including NASA/Ames, the University of Illinois, Colorado State University, the University of Wisconsin, and the University of Massachusetts. This work was supported by DOE’s Office of Science, Climate Change Research Division.