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From ground, air, and space, IU geographers hope to refine climate science data

Indiana University Bloomington geographers have received funding from NASA to study the accuracy of satellite data used in climate change research.

Forest productivity measurement

Images by NASA, Faiz Rahman lab

As part of IU Bloomington geographer Faiz Rahman's project to measure four forests' productivity in different climate conditions, he and his collaborators will collect data from NASA's MODIS satellite (top), from a plane equipped with a specially designed device (middle, behind the front wheel), and from towers within the forests themselves (bottom)

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The $527,000, three-year project is led by Faiz Rahman, an expert on the use of satellite data to study complex terrestrial ecosystems. Rahman's co-principal investigators are Danilo Dragoni, geography assistant scientist, and postdoctoral fellow Daniel Sims.

The relationship between reflected light (visible and otherwise) and the health or activity of forests, lakes and oceans is well established. Two forests of similar composition can produce vastly different intensities of a given range of light wavelengths, and these differences often indicate how productive the forests are. This information is used by a wide range of climate scientists and ecologists to understand how temperature and weather changes are influencing the use of carbon -- the productivity or health -- of natural resources.

"This is an integral part of global climate change," Rahman said. "We still do not know how much carbon different forests are taking in, and this is one of the last issues to be resolved in climate change discussion. What will be the impact of changing climate on carbon absorption and carbon production? This issue connects directly to global change, and will make it easier for us to predict what will happen so we can make intelligent decisions."

Faiz Rahman

Photo courtesy of the Faiz Rahman lab

Geographer Faiz Rahman

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Satellites are frequently used to collect light data from Earth's surface for analysis, but questions about the accuracy or usefulness of this data in recent years convinced Rahman, Dragoni, and Sims that a comparison of satellite and near-to-surface data is needed. Of particular concern is the relative tradeoff between spatial and temporal resolutions of satellite data. The images of Earth produced by NASA's MODIS satellite, for example, cover the whole Earth twice every day-- but lack spatial details at the forest canopy level.

The ambitious IU Bloomington project will gather data from four forests at three heights, simultaneously. During a crucial 30-minute window, NASA's MODIS satellite will fly over a target forest, providing images from low Earth orbit (about 420 miles above sea level). During that same half-hour, project scientists will gather information about forest productivity from airplane fly-overs at 3,000 feet and from towers within the forest canopies. The chartered airplane will be specially fitted with equipment that simulates satellite imaging systems, but at much higher spatial resolution.

The scientists plan 600 data-gathering days over the next three years, about 150 days per forest. The scientists chose as their study sites Morgan-Monroe State Forest (Ind.), Duke Forest (N.C.), Harvard Forest (Mass.) and Howland Forest (Maine) because these experimental sites represent the differences in the composition and productivity of Eastern U.S. forests.

"We will apply different models to these data," Rahman said. "We plan to compare satellite to ground-based to airplane data, and see if there are discrepancies, and if there are, try to figure out why. This research will hopefully give us a better understanding of the carbon balance of Eastern U.S. forests, and the impacts of global change on these forests."