Smoke over Athens

The effects of forest fires show up in a multi-satellite view of pollution. 


ON THE TAIL of three scorching heat waves in the summer of 2007, massive forest fires broke out across Greece and destroyed thousands of acres of forest, olive groves, and farmland. Heavy plumes of smoke billowed from burning forest canopies, and ash from the fires dusted ancient and modern buildings in nearby cities and towns. Numbering 3,000 from June to early September, the fires were the worst that Greece had seen in fifty years.

Athens is already one of the most polluted cities in Europe, more so in the summer when humidity and the intense Mediterranean sun heat up industrial and vehicular pollutants lingering in the atmosphere. Did the forest fires cause the city’s air pollution levels to get worse? Researchers in Greece could not answer this question easily. Most of the fires burned in rural areas where there were no ground-based instruments to measure pollution. The fires also produced gigantic smoke plumes that blew hundreds of miles from inland, across coastlines, and on to the Ionian Sea. These plumes were difficult to study using available ground monitoring networks alone.

The Greek government turned to the Harvard School of Public Health for help. Yang Liu studies air quality using remote sensing data and was a research associate there at the time of the Greek fires. He said, “The best tool was satellite remote sensing. We happened to have cloud-free days during most of the fire episodes, and that was ideal for satellites to observe the transport and the evolution of those plumes.” Liu, now an assistant professor at Emory University’s Rollins School of Public Health, knew that satellite sensors were a fairly new information source for air pollution studies. But he suspected that the right combination of satellite sensors could reveal how the forest fires affected Athens’ already fragile air quality.

Originally published in Sensing Our Planet: NASA Earth Science Research Features. Read the full story here.

Image courtesy V. Berger.