Insight into Saharan dust migration

Terra Daily via SPX:  Satellite pictures of Saharan dust clouds have been in the news all summer, but to Shankar Chellam, they have just raised more questions. How much impact did the Saharan dust have on Houston's air? Is it more toxic than our home-grown dust?

...Clouds of African dust often migrate across the Atlantic Ocean during summer months, affecting Houston's air quality from mid-June through mid-September. Chellam said it's especially prevalent in late August and early September. The dust, whipped up by sandstorms in northwest Africa and carried by trade winds across the Atlantic Ocean, takes about 10 days to two weeks to reach the United States and, ultimately, Houston.

...Chellam became interested after he noticed "the most curious coincidence" as he was collecting data on industrial air pollution outside plants along the Houston Ship Channel in 2008. He began the project expecting that the plants would emit a constant amount of pollution, as measured from just beyond their property lines. But he discovered that on some days they emitted relatively little, while emissions were much higher on other days.

"What we quickly realized was that the impact of the refineries varied with time," he said. "We naively had gone into our research expecting that if we took three months of data, we would get an average." A five-day period in July and August 2008 showed a large variation. That coincided with an influx of Saharan dust, Chellam said.

To determine the actual impact of the Saharan dust required scientific detective work. Chellam and his team determined the "fingerprint" of the African dust, allowing them to differentiate it from other types of pollutants in their samples: industrial dust, vehicle pollutants and smoke from wildfires, among other things....

Dust from the Sahara blowing over the Atlantic Ocean. Image from NASA