Washington – An international research consortium funded in part by the U.S. National Science Foundation (NSF) sent a fleet of aerial drones through pollution-filled skies over the Indian Ocean and achieved an important milestone in tracking pollutants responsible for dimming Earth's atmosphere.

The research also was funded by the National Oceanic and Atmospheric Administration, NASA, the United Nations Environmental Programme and the Republic of Maldives.

Researchers hope the data produced during the March flights will reveal in unprecedented detail how pollution particles cause dimming and contribute to the formation of clouds that amplify the dimming caused by the pollution.

The instrument-bearing autonomous unmanned aerial vehicles (AUAVs) completed 18 data-gathering missions near the Maldives, an island chain nation south of India, said scientist V. (Ram) Ramanathan of the Scripps Institution of Oceanography at the University of California in San Diego.

Ramanathan led a consortium of academic and industrial partners in developing aircraft and integrating them with miniaturized instruments that can capture aerosol-cloud-solar radiation data in remote regions once considered unobtainable.

During the Maldives AUAV Campaign (MAC), groupings of three aircraft were flown in a vertical (stacked) formation that allowed their onboard instruments to observe conditions below, inside and above clouds at the same time, according to an April 18 NSF press release.

"MAC has demonstrated that lightweight AUAVs and their miniaturized instruments are an effective and inexpensive means of simultaneously sampling clouds in polluted environments from within and from all sides," said Jay Fein, program director in NSF's Division of Atmospheric Sciences.

The research will help scientists determine how pollution affects cloud processes in weather and climate.

Such stacked flights with manned aircraft have been attempted, but rarely. The difficulty and cost of assembling and coordinating three similar aircraft have prevented the sort of repeated measurements needed to properly sample clouds.

"Based on MAC's success," Ramanathan said, "it is possible that in five years, hundreds of lightweight AUAVs will be documenting how human beings are polluting the planet and hopefully provide an early warning system for potential environmental disasters in the future."

The skies over the Indian Ocean reflect the range of human activities in South Asia, often in what are called atmospheric brown clouds – haze and cumulus clouds that can blanket the region.

The role that dust and aerosols from industrial, urban and agricultural emissions play in creating this brown haze is important to researchers who study climate change, especially how human activities could be changing the planet's reflectivity. Cloud cover cools Earth's surface by reflecting solar radiation back into space.

In recent years, researchers have realized that pollution in the atmosphere, and the dimming and cooling it causes, could be leading scientists to underestimate the true magnitude of global-warming trends.

Each AUAV has an instrument package weighing less than five kilograms. The packages include sensors for measuring solar radiation, cloud-drop size and concentrations, particle size and concentrations, turbulence, humidity and temperatures.

Flights took place between March 6 and March 31, taking off from an airport on the island of Hanimaadhoo in the Maldives.

Each AUAV tracked a separate component of brown cloud formation. The lowest, flying under the cloud, quantified the input of pollution particles and measured quantities of light that penetrated the clouds. The aircraft flying through the cloud measured the cloud's response to the introduction of particles.

The aircraft flying above the cloud measured the amount of sunlight reflected by the clouds into space and the export of particles out of the clouds.

The

(Distributed by the Bureau of International Information Programs, U.S. Department of State. Web site: http://usinfo.state.gov)

full text of the press release is available on the NSF Web site.