If you're sneezing right now, the cause may on the other side of the planet. In late June, winds began blowing what NASA describes as a "river of dust" from Africa across the Atlantic Ocean to North and South America.
Because of thermal expansion of the atmosphere around the equator, sand and dirt grains are suspended thousands of feet in the air, as a wind carries them westward.
Though Florida usually gets the heaviest dose of African dust, this year the dust seems to be spreading over a much wider swath of the south and southwest, according to Garrett Lewis, a meteorologist at TV News 5 in Fort Smith/Fayettsville, Ark.
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A study published in the Journal Environmental Science and Technology in 2008 found that the Saharan dust plume had the ability to double the atmospheric dust in Houston.
Dust events of this sort, which occur every year, can be a problem if you're an asthmatic or have respiratory problems. But the dust also can have some beneficial effects.
University of Miami researchers note that the suspended dust absorbs and scatters solar radiation over the tropical Atlantic, which can result in cooler ocean temperatures. That, in turn, may reduce the amount of energy available for hurricanes to form and strengthen.
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Additionally, the dust itself has value. Each year, about 40 million tons of Saharan dust ends up descending upon the Amazon River Basin, where it replenishes nutrients in the rainforest that have become depleted by tropical rains. The Everglades also has been fertilized for thousands of years by African dust as well.
But we may need to get accustomed to more long-range dust movement of this sort. It's not clear whether the region of Africa that generates the dust will become drier because of climate change, but if it does, more and more dust may end up sailing over the ocean to us.
Photo: A satellite image taken on June 25 captures a plume of dust from Africa moving across the Atlantic. Credit: NASA